build: Do not ignore logging.c in sc_prohibit_mkstemp

Now that the offending code was removed, we may remove this as well.

cfg.mk

@@ -817,5 +817,3 @@ exclude_file_name_regexp--sc_unmarked_diagnostics = \
   ^(docs/apibuild.py|tests/virt-aa-helper-test)$$
 
 exclude_file_name_regexp--sc_size_of_brackets = cfg.mk
-
-exclude_file_name_regexp--sc_prohibit_mkstemp = ^src/util/logging\.c$$