Add requests to requirements-to-freeze.txt

We're using requests directly in some code now (scrapers), so it should
be in here instead of just coming in as a dependency of other packages.
This also seems to fix some issues related to the version of urllib3
that gets automatically installed.

tildes/requirements-to-freeze.txt

@@ -30,6 +30,7 @@ pytest
 pytest-mock
 PyYAML  # needs to be installed separately for webassets
 qrcode
+requests
 sentry-sdk
 SQLAlchemy
 SQLAlchemy-Utils