Fix number of mirrors, fixes #1057

[maxnoe]

No description provided.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@b5c9913). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff            @@
##             master   #1061   +/-   ##
========================================
  Coverage          ?   83.2%           
========================================
  Files             ?     184           
  Lines             ?   10465           
  Branches          ?       0           
========================================
  Hits              ?    8707           
  Misses            ?    1758           
  Partials          ?       0

Impacted Files	Coverage Δ
ctapipe/io/simteleventsource.py	98.94% <ø> (ø)
ctapipe/io/tests/test_simteleventsource.py	100% <100%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b5c9913...7168956. Read the comment docs.