Fix spellcheck: Add 'Gunicorn' to dictionary

- Resolves spellcheck CI failure for Python Core SDK documentation
- Gunicorn is a legitimate Python WSGI HTTP Server name used in examples

Co-Authored-By: xin@statsig.com <xin@statsig.com>

Author: devin-ai-integration[bot]

cspell.json

@@ -76,6 +76,7 @@
     "GDPR",
     "Github",
     "GTM",
+    "Gunicorn",
     "IAM",
     "IDSync",
     "IDFA",