Fix flaky spec on test_file_name #2867 (#2868)

Author: keshavbiswa

test/faker/default/test_faker_file.rb

@@ -22,7 +22,7 @@ def test_mime_type_format_with_media_type
   end
 
   def test_file_name
-    assert_match %r{^([a-z\-_.]+)(\\|/)([a-z\-_]+)\.([a-z]+)$}, @tester
+    assert_match %r{^([a-z\-_.]+)(\\|/)([a-z\-_]+)\.([a-z0-9]+)$}, @tester
       .file_name
   end