gitk: Make the fake commit for the index changes green rather than magenta
gitk: Make the fake commit for the index changes green rather than magenta

The magenta was a bit close in color to the normal blue commits.  This
makes them green instead as suggested by Linus.

Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>
destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git