Potentially wrong version of bst-plugins-community used in CI

[doraskayo]

I noticed BST_PLUGINS_EXPERIMENTAL_VERSION is set here:

buildstream/.github/compose/ci.docker-compose.yml

Line 54 in 30145c6

BST_PLUGINS_EXPERIMENTAL_VERSION: master

I suspect it may need to be BST_PLUGINS_COMMUNITY_VERSION instead, if the intent was to affect this line:

buildstream/tox.ini

Line 59 in 30145c6

py{310,311,312,313,314}-plugins: git+https://gitlab.com/buildstream/buildstream-plugins-community.git@{env:BST_PLUGINS_COMMUNITY_VERSION:{[config]BST_PLUGINS_COMMUNITY_VERSION}}#egg=bst_plugins_community[deb]