fix: CG-10581 handle 404 github exception get_contents (#181)

Author: christinewangcw

src/codegen/git/clients/git_repo_client.py

@@ -82,6 +82,11 @@ def get_contents(self, file_path: str, ref: str | None = None) -> str | None:
         except UnknownObjectException:
             logger.info(f"File: {file_path} not found in ref: {ref}")
             return None
+        except GithubException as e:
+            if e.status == 404:
+                logger.info(f"File: {file_path} not found in ref: {ref}")
+                return None
+            raise
 
     def get_last_modified_date_of_path(self, path: str) -> datetime:
         """Uses the GitHub API to return the last modified date of a given directory or file.