Fix CameraFrame transformations for arrays of focal_length, fixes #1850

[maxnoe]

No description provided.

[codecov]

Codecov Report

Merging #1851 (0ffd358) into master (d7f8a58) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1851   +/-   ##
=======================================
  Coverage   92.22%   92.23%           
=======================================
  Files         190      190           
  Lines       15196    15202    +6     
=======================================
+ Hits        14015    14021    +6     
  Misses       1181     1181           

Impacted Files	Coverage Δ
ctapipe/coordinates/camera_frame.py	86.30% <100.00%> (ø)
ctapipe/coordinates/tests/test_coordinates.py	100.00% <100.00%> (ø)

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