drop warning re Apple patch - used by CI for quite a while now

so if there inconsistencies found between GNU patch and Apple's patch,
those are detected early and won't make it to master in the first
place.
macOS switched the system patch in macOS ventura (macOS 13), so older
systems have gnu patch, and ce31e09a6d40295cec4be9da8f4cec886d6c92c1
enabled to use the "new and unknown" apple patch that was pickier re
the context lines, but no other compatibility issues were observed.
So fine to say that it works fine/is no longer "experimental" but
rather the default on macOS

Change-Id: I993d4474beeb3840039363dc8fc2a401b188ca98
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/182820
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Tested-by: Jenkins

configure.ac

@@ -12109,7 +12109,6 @@ if test "$_os" = "SunOS" -o "$_os" = "Darwin" -o "$_os" = "FreeBSD"; then
     else
         if $GNUPATCH --version | grep "2\.0-.*-Apple" >/dev/null 2>/dev/null; then
             AC_MSG_RESULT([no, but accepted (Apple patch)])
-            add_warning "patch utility is not GNU patch. Apple's patch should work OK, but it might experience issues where GNU patch doesn't."
         else
             AC_MSG_ERROR([no, GNU patch needed. install or specify with --with-gnu-patch=/path/to/it])
         fi