Merge branch 'jc/test-i18ngrep'

With release 2.44 we got rid of all uses of test_i18ngrep and there
is no in-flight topic that adds a new use of it.  Make a call to
test_i18ngrep a hard failure, so that we can remove it at the end
of this release cycle.

* jc/test-i18ngrep:
  test_i18ngrep: hard deprecate and forbid its use

t/test-lib-functions.sh

@@ -1263,9 +1263,8 @@ test_cmp_bin () {
 	cmp "$@"
 }
 
-# Deprecated - do not use this in new code
 test_i18ngrep () {
-	test_grep "$@"
+	BUG "do not use test_i18ngrep---use test_grep instead"
 }
 
 test_grep () {