fix yaml warning: specify the loader to avoid arbitrary code execution (security)

more info:
https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation
6 jobs for CI_warnings in 29 minutes and 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Style
passed #37200
check_style

00:00:17

 
  Tests
failed #37370
run_tests:source

00:29:38

32.0%
failed #37247
run_tests:source

00:35:30

29.0%
failed #37201
run_tests:source

00:30:13

32.0%
 
  Build
skipped #37202
create_doc:reference
skipped #37203
create_doc:user
 
Name Stage Failure
failed
run_tests:source Tests
        2    0.000    0.000    1.410    0.705 /builds/bliss/bliss/bliss/scanning/acquisition/mca.py:230(_hard_reading)
39 0.003 0.000 25.688 0.659 /builds/bliss/bliss/bliss/common/task.py:32(__call__)
916 0.024 0.000 578.769 0.632 /builds/bliss/bliss/bliss/config/static.py:384(__init__)
924 0.766 0.001 582.793 0.631 /builds/bliss/bliss/bliss/config/static.py:394(reload)
2 0.000 0.000 1.252 0.626 /builds/bliss/bliss/bliss/common/motor_config.py:75(reload)
25 0.000 0.000 14.213 0.569 /builds/bliss/bliss/bliss/scanning/acquisition/motor.py:119(start)
25 0.003 0.000 13.579 0.543 /builds/bliss/bliss/bliss/scanning/acquisition/motor.py:128(_start_move)
13 0.001 0.000 7.019 0.540 /builds/bliss/bliss/bliss/scanning/acquisition/mca.py:246(_soft_reading)
ERROR: Job failed: exit code 1