Removed parameter 'request-concurrency'.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>

tests/CI_docker/build_testsuite_image.sh

@@ -47,6 +47,5 @@ gitlab-ci-multi-runner register \
   --run-untagged='true' \
   --locked='true' \
   --access-level='not_protected' \
-  --docker-pull-policy='never' \
-  --request-concurrency=4"
+  --docker-pull-policy='never'
 ls