Merge branch 'fix/linter' into 'master'

fix: don't interfere with stdout/stderr in linter

See merge request wpdesk/gitlab-ci!223

includes/tests/lint.yml

@@ -2,7 +2,7 @@
   stage: tests
   script:
     - composer install --no-dev
-    - find -name '*.php' -print0 | xargs -n1 -0 -P16 php -l 2>/dev/null
+    - find -name '*.php' -print0 |xargs -n1 -0 -P16 php -l |grep -v "No syntax errors detected"
 
 lint:8.1:
   <<: *lint-tmpl