Add back urllib3 pin (#16495)

## Summary & Motivation

Removed this earlier today and BK did not complain. Now it seems to be
complaining again, so adding it back.

## How I Tested These Changes

BK

.buildkite/dagster-buildkite/setup.py

@@ -22,6 +22,9 @@
         "requests",
         "typing_extensions>=4.2",
         "pathspec",
+        # Need this until we have OpenSSL 1.1.1+ available in BK base image
+        # Context: https://github.com/psf/requests/issues/6432
+        "urllib3<2",
     ],
     entry_points={
         "console_scripts": [