Merge branch 'jc/test-i18ngrep'

Another step to deprecate test_i18ngrep.

* jc/test-i18ngrep:
  tests: teach callers of test_i18ngrep to use test_grep
  test framework: further deprecate test_i18ngrep

t/t4053-diff-no-index.sh

@@ -56,7 +56,7 @@ test_expect_success 'git diff --no-index executed outside repo gives correct err
 		export GIT_CEILING_DIRECTORIES &&
 		cd non/git &&
 		test_must_fail git diff --no-index a 2>actual.err &&
-		test_i18ngrep "usage: git diff --no-index" actual.err
+		test_grep "usage: git diff --no-index" actual.err
 	)
 '