LibRegex: Use match_ordinary_characters() in ECMA262Parser::parse_atom()

Otherwise we would only match TokenType::Char, making all of these invalid:

- /foo,bar/
- /foo\/bar/
- /foo=bar/
- /foo-bar/
- /foo:bar/

Fixes #4243.

Libraries/LibRegex/Tests/Regex.cpp

@@ -488,6 +488,7 @@ TEST_CASE(ECMA262_parse)
         "^[\\w+/_-]+[=]{0,2}$",                        // #4189
         "^(?:[^<]*(<[\\w\\W]+>)[^>]*$|#([\\w\\-]*)$)", // #4189
         "\\/",                                         // #4189
+        ",/=-:",                                       // #4243
         "\\x",                                         // Even invalid escapes are allowed if ~unicode.
     };