Fix deprecation warning about variants and formats

- After rails#35408 and
  rails#35406, the `formats` and
  `variants` methods are deprecated in favor of `format` and `variant`.

Author: prathamesh-sonpatki

actionview/test/template/testing/fixture_resolver_test.rb

@@ -24,7 +24,7 @@ def test_should_match_templates_with_variants
     assert_equal 1, templates.size, "expected one template"
     assert_equal "this text",       templates.first.source
     assert_equal "arbitrary/path",  templates.first.virtual_path
-    assert_equal [:html],           templates.first.formats
-    assert_equal ["variant"],       templates.first.variants
+    assert_equal :html,           templates.first.format
+    assert_equal "variant",       templates.first.variant
   end
 end