Cleanup python version properties

Now that python 2 is fully removed, there's no need for
version-specific properties. Remove them.

Also remove usages of embedded_launcher: true, as that
is the new default value.

Bug: 399954452
Test: Presubmits
Change-Id: Ie37f6b3bdb8e16db92078938df2a8cb2b9e5d3a8
1 file changed