t7800 (difftool): add missing &&
t7800 (difftool): add missing &&

Also remove a call to 'git config --unset difftool.prompt', since that is
already unset by restore_test_defaults.

Acked-by: Ævar Arnfjörð Bjarmason <0135fcc047f75af264c800977a73e353c6ba842d@gmail.com>
Reviewed-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
Signed-off-by: Elijah Newren <955405675e5ddb1a110d200661c528aa223ef60f@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git