🔥 remove Cirrus CI jobs

[burgholzer]

Description

cda-tum/mqt-core#553 transitioned the reusable MQT workflows from Cirrus CI back to GitHub Actions.
As such, the remaining Cirrus CI workflows can be removed.

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[burgholzer]

A corresponding CD run can be seen here: https://github.com/cda-tum/mqt-qmap/actions/runs/7991506462

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b7c3168) 89.7% compared to head (c794732) 89.7%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #430     +/-   ##
=======================================
- Coverage   89.7%   89.7%   -0.1%     
=======================================
  Files         61      61             
  Lines       6362    6362             
  Branches    1008    1008             
=======================================
- Hits        5710    5709      -1     
- Misses       652     653      +1     

Flag	Coverage Δ		*Carryforward flag
cpp	89.3% <ø> (ø)		Carriedforward from b7c3168
python	94.7% <ø> (-0.3%)	⬇️

*This pull request uses carry forward flags. Click here to find out more.

see 1 file with indirect coverage changes