update to Pex 2.33.1

Release: https://github.com/pex-tool/pex/releases/tag/v2.33.1

```
Lockfile diff: 3rdparty/python/user_reqs.lock [python-default]

==                    Upgraded dependencies                     ==

  cryptography                   44.0.0       -->   44.0.1
  pex                            2.33.0       -->   2.33.1
  websockets                     14.2         -->   15.0
```

3rdparty/python/requirements.txt

@@ -11,7 +11,7 @@ freezegun==1.2.1
 ijson==3.2.3
 libcst==1.4.0
 packaging==21.3
-pex==2.33.0
+pex==2.33.1
 psutil==5.9.8
 # This should be compatible with pytest.py, although it can be looser so that we don't
 # over-constrain pantsbuild.pants.testutil