python packagisation: Remove misleading "For backward compat" comments
python packagisation: Remove misleading "For backward compat" comments

`stbt.get_config` is still the official public API. Splitting stbt.py
into a python package with sub-packages is --so far-- purely an internal
organisation / tidiness exercise.

LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester