cocci rules: remove unused "F" metavariable from pending rule

Fix an issue with a rule added in 9b45f49 (object-store: prepare
has_{sha1, object}_file to handle any repo, 2018-11-13). We've been
spewing out this warning into our [email protected] since that rule was added:

	warning: rule starting on line 21: metavariable F not used in the - or context code

We should do a better job of scouring our coccinelle log files for
such issues, but for now let's fix this as a one-off.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: avar

contrib/coccinelle/the_repository.pending.cocci

@@ -20,7 +20,6 @@ expression E;
 
 @@
 expression E;
-expression F;
 @@
 - has_object_file_with_flags(
 + repo_has_object_file_with_flags(the_repository,