add mypy ignore for referencing

causing errors:
/home/runner/.cache/pypoetry/virtualenvs/humanloop-3enmfHET-py3.9/lib/python3.9/site-packages/referencing/_core.py:565: error: Invalid "type: ignore" comment  [syntax]
/home/runner/.cache/pypoetry/virtualenvs/humanloop-3enmfHET-py3.9/lib/python3.9/site-packages/referencing/_core.py:566: error: Invalid "type: ignore" comment  [syntax]

Author: harry-humanloop

mypy.ini

@@ -2,4 +2,8 @@
 exclude = (?x)(
     ^src/humanloop/eval_utils/.*\.py$  # all files in "eval_utils" folder
     | ^src/humanloop/prompt_utils\.py$  # single "prompt_utils.py" file
-  )
+  )
+
+# Add ignore for referencing package
+[mypy-referencing.*]
+ignore_errors = True