.gitignore: remove dangling file

The library was removed 7 years ago on commit ae34ac126f. But not from
the .gitignore file.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitignore

@@ -135,7 +135,6 @@
 /git-remote-ftps
 /git-remote-fd
 /git-remote-ext
-/git-remote-testpy
 /git-repack
 /git-replace
 /git-request-pull