git-gui: CTRL/CMD + numpad ENTER does not invoke same command as "regular" ENTER

[Birger Skogeng Pedersen <birgersp@xxxxxxxxx>]

In git-gui, we can hit CTRL/CMD+ENTER to create a commit. However,
using the numpad ENTER does not invoke the same command.

I propose that both numpad ENTER and "regular" ENTER should invoke the
same command.