[FIX] web: Locale not loaded for Serbian lang

In Serbia there are two language codes and those are `sr_RS` (Cyrillic) and `sr@latin` (Latin). Inside of the `web/static/lib/moment/locale` folder, the two langs are registered as `sr-cyrl.js` and `sr.js` respectively. The `load_locale` controller wasn't loading the right langs for neither case.

X-original-commit: 65d5ab801f22b42a0f94fe4b86f68ace451ea184
Part-of: odoo/odoo#114565

addons/web/controllers/webclient.py

@@ -29,10 +29,17 @@ def CONTENT_MAXAGE():
     return http.STATIC_CACHE_LONG
 
 
+MOMENTJS_LANG_CODES_MAP = {
+    "sr_RS": "sr_cyrl",
+    "sr@latin": "sr"
+}
+
+
 class WebClient(http.Controller):
 
     @http.route('/web/webclient/locale/<string:lang>', type='http', auth="none")
     def load_locale(self, lang):
+        lang = MOMENTJS_LANG_CODES_MAP.get(lang, lang)
         magic_file_finding = [lang.replace("_", '-').lower(), lang.split('_')[0]]
         for code in magic_file_finding:
             try: