[Fix] image creation via Dockerfile after move to Python 3.11

[jstourac]

This is a followup of [1,2] and fixes image build creation after we moved from Python 3.9 to Python 3.11

On top of that, it also removes dnf cache after all installation is done. There is no change in the sice of resulting image but it's a standard step to do in the Dockerfiles in general.

[1] #1118
[2] 867a617

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$ podman run --entrypoint /bin/bash --rm -it 38021db38acc
bash-5.1# poetry install
The currently activated Python version 3.9.18 is not supported by the project (>=3.11.5, <3.12.0).
Trying to find and use a compatible version. 
Using python3.11 (3.11.7)
Installing dependencies from lock file

No dependencies to install or update

Installing the current project: ods-ci (0.1.0)
bash-5.1# poetry run robot --help
The currently activated Python version 3.9.18 is not supported by the project (>=3.11.5, <3.12.0).
Trying to find and use a compatible version. 
Using python3.11 (3.11.7)
Robot Framework -- A generic automation framework

Version:  6.1.1 (Python 3.11.7 on linux)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %
405	0	0	405	100