Removing workaround for git submodules

The upstream bug is fixed, the workaround is not necessary anymore.

.gitlab-ci.yml

 ---
 variables:
-# work around https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/issues/2148
-# value should be "recursive" without workaround
-  GIT_SUBMODULE_STRATEGY: none
+  GIT_SUBMODULE_STRATEGY: recursive
 
 before_script:
 - echo "Running make concurrently with $(nproc) cores, where possibly"
-# make sure we can update submodules and apply the patches
-- git submodule foreach --recursive git reset --hard HEAD
-- git submodule foreach --recursive git clean -fdx
-# work around https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/issues/2148
-- git submodule sync --recursive
-- git submodule update --init --recursive
-# end workaround
 - patches/apply_patches.sh
 # detect number of processors, but make sure never to run with -j"", as the
 # build host would likely run out of memory