fix: relaxes gh types (#519)

Author: jayhack

src/codegen/extensions/github/types/events/push.py

@@ -24,4 +24,4 @@ class PushEvent(BaseModel):
     base_ref: str | None = None
     compare: str
     commits: list[GitHubCommit]
-    head_commit: GitHubCommit
+    head_commit: GitHubCommit | None = None

src/codegen/extensions/github/types/pull_request.py

@@ -43,7 +43,7 @@ class PullRequest(BaseModel):
     updated_at: str
     closed_at: Optional[str]
     merged_at: Optional[str]
-    merge_commit_sha: str
+    merge_commit_sha: Optional[str]
     assignee: Optional[GitHubUser]
     assignees: list[GitHubUser]
     requested_reviewers: list[GitHubUser]