Rm Github Import (#8257)

It's not a required dep but would break peoples builds

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/langchain/langchain/utilities/github.py

@@ -1,12 +1,16 @@
 """Util that calls GitHub."""
+from __future__ import annotations
+
 import json
-from typing import Any, Dict, List, Optional
+from typing import TYPE_CHECKING, Any, Dict, List, Optional
 
-from github.Issue import Issue
 from pydantic import BaseModel, Extra, root_validator
 
 from langchain.utils import get_from_dict_or_env
 
+if TYPE_CHECKING:
+    from github.Issue import Issue
+
 
 class GitHubAPIWrapper(BaseModel):
     """Wrapper for GitHub API."""