🚨 fix a couple of compiler warnings

[burgholzer]

Description

This small PR fixes a handful of compiler warnings that popped up during updating mqt-qmap.

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.2%. Comparing base (e3f8ee1) to head (dd2bc96).

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #578   +/-   ##
=====================================
  Coverage   91.2%   91.2%           
=====================================
  Files        132     132           
  Lines      13904   13904           
  Branches    2203    2203           
=====================================
  Hits       12692   12692           
  Misses      1212    1212           

Flag	Coverage Δ
cpp	90.9% <100.0%> (ø)
python	99.5% <ø> (ø)

Files	Coverage Δ
src/dd/NoiseFunctionality.cpp	97.1% <100.0%> (ø)