Upgrade TensorFlow to version 2.11.*

[osma]

We are currently using TensorFlow 2.9.1, which has reported vulnerabilities. Also dependabot is complaining about them. It would be trivial to upgrade to 2.9.3, where those issues have been fixed.

But instead, I tested upgrading directly to 2.11.0. Everything seems to work fine with this new version. I also tested a small model that was trained on 2.9.1, before the upgrade, and it worked perfectly well.

I pinned this as 2.11.* so that upgrading to patch releases is allowed in the future.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[codecov[bot]]

Codecov Report

Base: 99.55% // Head: 99.55% // No change to project coverage :thumbsup:

Coverage data is based on head (0c70c25) compared to base (26a405c). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #651 +/- ## ======================================= Coverage 99.55% 99.55% ======================================= Files 87 87 Lines 6006 6006 ======================================= Hits 5979 5979 Misses 27 27 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=NatLibFi). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=NatLibFi)

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[osma]

On second thought, I think this is fine and basically a minimal upgrade, I'll merge it as is.