Use proper exit code for composer lint

[MorrisJobke]

See nextcloud/server#20952

[codecov-io]

Codecov Report

Merging #1034 into master will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #1034      +/-   ##
============================================
- Coverage     39.96%   39.95%   -0.02%     
  Complexity      861      861              
============================================
  Files            59       59              
  Lines          3195     3196       +1     
============================================
  Hits           1277     1277              
- Misses         1918     1919       +1     

Impacted Files	Coverage Δ	Complexity Δ
lib/Controller/BookmarkController.php	37.63% <0.00%> (-0.14%)	99.00 <0.00> (ø)

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[marcelklehr]

Seems to work.