Fix failing "updated deps" test-runs by upping phpstan/phpstan to latest

Problem/Motivation

With the 1.10.3 release of phpstan/phpstan, we see our "updated deps" test-runs fail on both 10.0.x and 10.1.x

Steps to reproduce

https://www.drupal.org/node/3060/qa →

Proposed resolution

- Bump phpstan/phpstan to 1.`10.3 (including upping the version constraint in composer.json) AND refresh the baseline at the same time.
- Create a follow-up to deal with the, basically all the same, new baseline suppressions.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet