Remove obsolete autoninja.bat comment

A long time ago autoninja.bat had to avoid using Python 3 because of
problems with git bash. Those days are long past. We don't use Python 2
anymore. So I am removing the comment.

The comment was added in crrev.com/c/2634201 in 2021.

Change-Id: Ia3d3db495937478979c45cdc2c3443fd31620805
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5014576
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>

autoninja.bat

@@ -25,10 +25,6 @@ if not defined AUTONINJA_BUILD_ID (
 if "%NINJA_SUMMARIZE_BUILD%" == "1" set "NINJA_STATUS=[%%r processes, %%f/%%t @ %%o/s : %%es ] "
 
 :: Execute autoninja.py and pass all arguments to it.
-:: Don't use python3 because it doesn't work in git bash on Windows and we
-:: should be consistent between autoninja.bat and the autoninja script used by
-:: git bash.
-
 @call %scriptdir%\vpython3.bat %scriptdir%autoninja.py "%%*"
 @if errorlevel 1 goto buildfailure