Pin PIP version for pip-compile job

This commit pins `pip==22.0.0` in the `tox` environment `pip-compile` as
later versions of it are not properly working, causing the following
failure when running the scheduled CI via GH Actions:

```
AttributeError: 'function' object has no attribute 'cache_clear'
```

Signed-off-by: Jonathan Gangi <[email protected]>

Author: JAVGan

tox.ini

@@ -15,7 +15,9 @@ commands=
 [testenv:pip-compile]
 basepython = python3.9
 skip_install = true
-deps = pip-tools
+deps =
+    pip-tools
+    pip==22.0.0
 commands = 
     pip-compile -U --generate-hashes --reuse-hashes --output-file=requirements.txt
     pip-compile -U --generate-hashes --reuse-hashes --output-file=requirements-test.txt setup.py requirements-test.in