object-store.h: remove unused has_sha1_file*()

These macros were last used in 5d3679ee02 (sha1-file: drop
has_sha1_file(), 2019-01-07), so let's remove coccinelle migration
rules added 9b45f49981 (object-store: prepare has_{sha1, object}_file
to handle any repo, 2018-11-13), along with the compatibility macros
themselves.

The "These functions.." in the diff context and the general comment
about compatibility macros still applies to
"NO_THE_REPOSITORY_COMPATIBILITY_MACROS" use just a few lines below
this, so let's keep the comment.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/coccinelle/the_repository.pending.cocci

@@ -11,21 +11,6 @@ expression G;
 + repo_read_object_file(the_repository,
   E, F, G)
 
-@@
-expression E;
-@@
-- has_sha1_file(
-+ repo_has_sha1_file(the_repository,
-  E)
-
-@@
-expression E;
-expression F;
-@@
-- has_sha1_file_with_flags(
-+ repo_has_sha1_file_with_flags(the_repository,
-  E)
-
 @@
 expression E;
 @@