chore(types): delete five type: ignore comments that suppress nothing

mypy's warn_unused_ignores is on, so these were reported as errors in
their own right — a suppression that no longer suppresses is a claim
that something is broken when it is not, and it silently widens to
cover a real error if one later appears on that line.

Two carried a "Forward reference" note that is still accurate; the note
is kept and only the ignore removed.

95 errors -> 90. Comment-only, so no runtime behaviour can have changed
and the suite was not re-run for this commit. The `# type: ignore` count
across the tree drops from 6 to 1, which is the anchor for the rest of
this work: clearing a type error by suppressing it would push that
number the other way.

Co-Authored-By: Claude <noreply@anthropic.com>

src/responses/schemas.py

@@ -71,7 +71,7 @@ class FunctionCallOutputItem(CustomBaseModel):
 
 # Union type for all output items
 # Type: ignore because Pydantic handles union types specially
-OutputItem = MessageOutputItem | ReasoningOutputItem | FunctionCallOutputItem  # type: ignore
+OutputItem = MessageOutputItem | ReasoningOutputItem | FunctionCallOutputItem
 
 
 # ============================================================================