request-pull: capitalise "Git" to make it a proper noun

request-pull: capitalise "Git" to make it a proper noun

Of the many ways to spell the three-letter word, the variant "Git"
should be used when referring to a repository in a description; or, in
general, when it is used as a proper noun.

We thus change the pull-request template message so that it reads

   "...in the Git repository at:"

Besides, this brings us in line with the documentation, see
Documentation/howto/using-signed-tag-in-pull-request.txt

Signed-off-by: Ann T Ropea <redacted>
Acked-by: Jonathan Nieder <redacted>
Reviewed-by: Jonathan Nieder <redacted>
Signed-off-by: Junio C Hamano <redacted>