Remove Travis CI

[madhurgupta10]

Description
Fixes #4091

Removed Travis CI and Badge

[codecov]

Codecov Report

Merging #4641 (cfc3037) into master (b9273b0) will increase coverage by 0.32%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #4641      +/-   ##
============================================
+ Coverage     44.28%   44.61%   +0.32%     
  Complexity      376      376              
============================================
  Files           131      131              
  Lines          2468     2468              
  Branches        272      272              
============================================
+ Hits           1093     1101       +8     
+ Misses         1285     1277       -8     
  Partials         90       90              

Impacted Files	Coverage Δ
...r/free/nrw/commons/explore/media/MediaConverter.kt	90.24% <0.00%> (+19.51%)	⬆️

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[neslihanturan]

Thanks a lot @madhurgupta10 :)