pre-commit: move prospector inside pre-commit

- removes `prospector` check from tox
- run `prospector` check inside pre-commit

This allows developers to auto-run prospector _before_ pushing changes to GitHub
and be able to fix these problems locally in a quicker way.

Author: humitos

.github/workflows/pip-tools.yaml

@@ -39,9 +39,6 @@ jobs:
       - name: Run pip-compile on requirements/testing.in
         run: pip-compile --upgrade --resolver=backtracking --output-file=requirements/testing.txt requirements/testing.in
 
-      - name: Run pip-compile on requirements/lint.in
-        run: pip-compile --upgrade --resolver=backtracking --output-file=requirements/lint.txt requirements/lint.in
-
       - name: Run pip-compile on requirements/docs.in
         run: pip-compile --upgrade --resolver=backtracking --output-file=requirements/docs.txt requirements/docs.in