[pre-commit] Use --python-version for mypy instead of forcing a python interpreter (#12869)

Author: Pierre-Sassoulas

Diff for: .pre-commit-config.yaml

@@ -32,8 +32,7 @@ repos:
     hooks:
     -   id: mypy
         files: ^(src/|testing/|scripts/)
-        args: []
-        language_version: "3.8"
+        args: ["--python-version=3.8"]
         additional_dependencies:
           - iniconfig>=1.1.0
           - attrs>=19.2.0