Use safe loading for YAML config file

[pnuu]

Pyyaml 6.0 requires the loader to be defined for YAML reading. This PR switches from yaml.load() to yaml.safe_load() for reading the config file.

• Tests passed
• Passes git diff origin/main **/*py | flake8 --diff

[codecov]

Codecov Report

Merging #64 (47dc595) into main (ee08e0f) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main      #64   +/-   ##
=======================================
  Coverage   46.49%   46.49%           
=======================================
  Files          15       15           
  Lines        2540     2540           
=======================================
  Hits         1181     1181           
  Misses       1359     1359           

Impacted Files	Coverage Δ
trollsched/utils.py	15.47% <0.00%> (ø)

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[mraspaud]

LGTM