community[patch]: Fix github search issues and PRs PaginatedList has no len() error (#16806)

**Description:** 
Bugfix: Langchain_community's GitHub Api wrapper throws a TypeError when
searching for issues and/or PRs (the `search_issues_and_prs` method).
This is because PyGithub's PageinatedList type does not support the
len() method. See https://github.com/PyGithub/PyGithub/issues/1476

![image](https://github.com/langchain-ai/langchain/assets/8849021/57390b11-ed41-4f48-ba50-f3028610789c)
  **Dependencies:** None 
  **Twitter handle**: @ChrisKeoghNZ
  
I haven't registered an issue as it would take me longer to fill the
template out than to make the fix, but I'm happy to if that's deemed
essential.

I've added a simple integration test to cover this as there were no
existing unit tests and it was going to be tricky to set them up.

Co-authored-by: Chris Keogh <chris.keogh@xero.com>

libs/community/tests/integration_tests/utilities/test_github.py

@@ -19,3 +19,9 @@ def test_get_open_issues(api_client: GitHubAPIWrapper) -> None:
     """Basic test to fetch issues"""
     issues = api_client.get_issues()
     assert len(issues) != 0
+
+
+def test_search_issues_and_prs(api_client: GitHubAPIWrapper) -> None:
+    """Basic test to search issues and PRs"""
+    results = api_client.search_issues_and_prs("is:pr is:merged")
+    assert len(results) != 0