Re-enable image.config test

[chapulina]

Resolves #40

I can't reproduce the test failure locally, hopefully it's working on CI as well, we'll see 🤞

[codecov]

Codecov Report

Merging #140 into ign-gui3 will decrease coverage by 2.49%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           ign-gui3     #140      +/-   ##
============================================
- Coverage     62.06%   59.57%   -2.50%     
============================================
  Files            19       20       +1     
  Lines          2312     2471     +159     
============================================
+ Hits           1435     1472      +37     
- Misses          877      999     +122     

Impacted Files	Coverage Δ
src/plugins/image_display/ImageDisplay.cc	23.27% <0.00%> (ø)

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[ahcorde]

LGTM, there is a Windows failure but it's unrelated:

  Target "ignition-transport8-log" links to target "ZeroMQ::ZeroMQ" but the
  target was not found.  Perhaps a find_package() call is missing for an
  IMPORTED target, or an ALIAS target is missing?