Merge "Update Python 3 migration note in Changes.md" into main

## Python 2 to 3 migration

The path set when running builds now makes the `python` executable point to python 3,

whereas on previous versions it pointed to python 2. If you still have python 2 scripts,

you can change the shebang line to use `python2` explicitly. This only applies for

scripts run directly from makefiles, or from soong genrules.

In addition, `python_*` soong modules no longer allow python 2.

Python 2 is slated for complete removal in V.

Python 2 has been completely removed from the build. Please migrate any remaining usages to

Python 3, and remove any version-specific properties from bp files.

## Stop referencing sysprop_library directly from cc modules