builtin-receive-pack.c: fix compiler warnings about format string

builtin-receive-pack.c: fix compiler warnings about format string

While all of the strings passed to warning() are, in fact, literals, the
compiler doesn't recognize them as such because it doesn't see through
the loop used to iterate over them:

   builtin-receive-pack.c: In function 'warn_unconfigured_deny':
   builtin-receive-pack.c:247: warning: format not a string literal and no format arguments
   builtin-receive-pack.c: In function 'warn_unconfigured_deny_delete_current':
   builtin-receive-pack.c:273: warning: format not a string literal and no format arguments

Calm the compiler by adding easily recognizable format string literals.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>