ALLOW mode does not check for masked JSON Paths ambiguity.

[andrebrait]

When in ALLOW mode, the JSONPaths added via maskJsonPaths(String, KeyMaskingConfig) are not checked for ambiguity because the check only checks the targetJsonPaths map:

        public JsonMaskingConfig build() {
            JSON_PATH_PARSER.checkAmbiguity(targetJsonPaths);  // <-- no checking for the key configs
            return new JsonMaskingConfig(this);
        }

I have never run into any issues because of this, but it looks like an oversight.