Upgrade actions/cache to v4

[bocytko]

Fix #968

Description

Upgrade action/cache to v4

Motivation and Context

See #968 for details.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[bocytko]

https://github.com/zalando/problem-spring-web/actions/runs/13348627714/job/37282266230

Post job cleanup.
/usr/bin/tar --posix -cf cache.tzst --exclude cache.tzst -P -C /home/runner/work/problem-spring-web/problem-spring-web --files-from manifest.txt --use-compress-program zstdmt
Sent [2](https://github.com/zalando/problem-spring-web/actions/runs/13348627714/job/37282266230#step:14:2)05895753 of 273004617 (75.4%), 196.2 MBs/sec
Sent 273004617 of 273004617 (100.0%), 250.6 MBs/sec
Cache saved with key: m2

[bocytko]

👍

[MALPI]

👍