Deprecate unused OpenLlama architecture (#24922)

* Resolve typo in check_repo.py

* Specify encoding when opening modeling files

* Deprecate the OpenLlama architecture

* Add disclaimer pointing to Llama

I'm open to different wordings here

* Match the capitalisation of LLaMA

utils/check_config_attributes.py

@@ -238,7 +238,7 @@ def check_config_attributes_being_used(config_class):
     modeling_sources = []
     for path in modeling_paths:
         if os.path.isfile(path):
-            with open(path) as fp:
+            with open(path, encoding="utf8") as fp:
                 modeling_sources.append(fp.read())
 
     unused_attributes = []