Update Heroku instructions in README

Since Heroku's Python builds now use `--enable-shared` (for Python 3.10 and newer), so use of custom builds or a custom buildpack is no longer required.

See:
heroku/heroku-buildpack-python#1320
https://github.com/heroku/heroku-buildpack-python/blob/928d0c593f6b6def16d6ad8451f56a997760eace/builds/build_python_runtime.sh#L117-L133

README.md

@@ -159,41 +159,16 @@ translates Ruby's coerce system into Python's swapped operation protocol.
 
 ## Deploying on Heroku
 
-Heroku's default version of Python is not compiled with the `--enabled-shared`
-option and can't be accessed by PyCall.
+Heroku's default builds of Python are now compiled with the `--enabled-shared` option
+(when using Python 3.10 and newer) and so work out of the box with PyCall without
+the need for a custom buildpack.
 
-There are many ways to make our heroku use Python that is compiled with the `--enabled-shared` option:
-
-  - use Heroku's official Python buildpacks `post_compile` hooks to recompile the python if the `--enabled-shared` option is not enabled.
-    example script of `post_compile` in ruby on rails app `bin/post_compile`.
-
-        set -e
-        buildpack_url=https://github.com/heroku/heroku-buildpack-python
-        buildpack_vsn=v197 # adjust version accordingly https://github.com/heroku/heroku-buildpack-python/tags
-
-        # rebuild python if it's missing enable-shared
-        if  ! python3 -msysconfig | grep enable-shared \
-            > /dev/null; then
-          PYTHON_VERSION="$(< runtime.txt)"
-          git clone -b "$buildpack_vsn" "$buildpack_url" _buildpack
-          export WORKSPACE_DIR="$PWD/_buildpack/builds"
-          rm -f .heroku/python/bin/python   # prevent failing ln after build
-          sed -i 's!figure --pre!figure --enable-shared --pre!' \
-            "$WORKSPACE_DIR"/runtimes/python3
-          "$WORKSPACE_DIR/runtimes/$PYTHON_VERSION" /app/.heroku/python/
-          rm -fr _buildpack
-        fi
-
-  - use your own precompiled python with `--enabled-shared` options then fork the official heroku [python buildspacks](https://github.com/heroku/heroku-buildpack-python) and change the `BUILDPACK_S3_BASE_URL` with your own uploaded precompiled python in Amazon's S3.
-  - use 3rd party buildpacks from the [markets](https://elements.heroku.com/buildpacks) that have python with `--enabled-shared` option.
-
-
-The buildpack will expect to find both a `runtime.txt` and a `requirements.txt` 
+The Python buildpack will expect to find both a `runtime.txt` and a `requirements.txt` 
 file in the root of your project. You will need to add these to specify the 
 version of Python and any packages to be installed via `pip`, _e.g_ to use 
 version Python 3.8.1 and version 2.5 of the 'networkx' package:
 
-    $ echo "python-3.8.1" >> runtime.txt
+    $ echo "python-3.12.6" >> runtime.txt
     $ echo "networkx==2.5" >> requirements.txt
 
 Commit these two files into project's repository. You'll use these to manage
@@ -212,12 +187,11 @@ For a Ruby/Rails application this will typically report the stock `heroku/ruby`
 buildpack, or possibly both `heroku/ruby` and `heroku/nodejs`. 
 
 Clear the list and progressively add back your buildpacks, starting with the Python 
-community-developed buildpack. For example, if `ruby` and `nodejs` buildpacks were 
-previously installed, and chosing the 'ReforgeHQ' buildback, your setup process will 
-be similar to this: 
+buildpack. For example, if `ruby` and `nodejs` buildpacks were previously installed,
+your setup process will be similar to this: 
 
     $ heroku buildpacks:clear
-    $ heroku buildpacks:add https://github.com/ReforgeHQ/heroku-buildpack-python -i 1
+    $ heroku buildpacks:add heroku/python -i 1
     $ heroku buildpacks:add heroku/nodejs -i 2
     # heroku buildpacks:add heroku/ruby -i 3
 
@@ -235,9 +209,6 @@ The Python bootstrapping process will appear in the log first, followed by the R
 and so on. PyCall should now be able to successfully call Python functions from 
 within the Heroku environment.
 
-NB It is also possible to specify buildpacks within Docker images on Heroku.
-See Heroku's [documentation on using Docker Images](https://devcenter.heroku.com/articles/build-docker-images-heroku-yml).
-
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies.