Fix numpy deprecation warning

[maxnoe]

No description provided.

[codecov]

Codecov Report

Merging #171 (83f0e06) into master (eafbe37) will increase coverage by 0.01%.
The diff coverage is 20.79%.

❗ Current head 83f0e06 differs from pull request most recent head a1f3bf0. Consider uploading reports for the commit a1f3bf0 to get more accurate results

@@            Coverage Diff             @@
##           master     #171      +/-   ##
==========================================
+ Coverage   63.15%   63.17%   +0.01%     
==========================================
  Files          21       21              
  Lines        2717     2713       -4     
==========================================
- Hits         1716     1714       -2     
+ Misses       1001      999       -2     

Impacted Files	Coverage Δ
ctaplot/gammaboard/reader.py	0.00% <0.00%> (ø)
ctaplot/plots/style.py	100.00% <ø> (ø)
ctaplot/gammaboard/gammaboard.py	11.92% <1.29%> (+0.01%)	⬆️
ctaplot/ana/ana.py	88.20% <89.47%> (-0.03%)	⬇️
ctaplot/__init__.py	100.00% <100.00%> (ø)
ctaplot/ana/tests/test_ana.py	100.00% <100.00%> (ø)
ctaplot/plots/plots.py	78.46% <100.00%> (ø)

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