chore(deps): cap websockets per-interpreter for Python 3.7/3.8/3.9

websockets raised its min Python in stages, so a flat >=16.1.1 floor is
uninstallable on 3.7/3.8/3.9. Split with python_version markers: old
interpreters keep their last compatible release, 3.10+ takes >=16.1.1,<17.

Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

Author: WilliamBergamin

requirements/optional.txt

@@ -28,8 +28,11 @@ boto3<=2
 SQLAlchemy>=2.0.51,<3
 
 # websockets
-# Note: websockets 9 is not compatible with Python 3.10; floor at 9.1.
-websockets>=16.1.1,<17
+# Note: websockets's minimum Python rose in stages (>=3.8 at 12.0, >=3.9 at 14.0, >=3.10 at 16.0); cap each old interpreter at its last compatible release.
+websockets>=9.1,<12; python_version == "3.7"
+websockets>=9.1,<14; python_version == "3.8"
+websockets>=9.1,<16; python_version == "3.9"
+websockets>=16.1.1,<17; python_version >= "3.10"
 
 # websocket-client
 websocket-client>=1,<2