add GIT_SUBMODULE_STRATEGY: recursive to .gitlab-ci.yml

2 jobs for master in 2 minutes and 11 seconds
Status Job ID Name Coverage
  Test
failed #39853
Linux
test-2.7

00:02:11

passed #39852
Linux
test-3.5

00:01:13

 
Name Stage Failure
failed
test-2.7 Test There is an unknown failure, please try again
  File "/local/gitlab-runner/builds/8e032315/0/adielen/openmesh-python/tests/test_trimesh_normal_calculations.py", line 81, in test_calc_vertex_normal_fast
self.assertTrue(np.allclose(n, np.array([1, 2, 0])))
AssertionError: False is not true

----------------------------------------------------------------------
Ran 110 tests in 0.376s

FAILED (failures=1, errors=25)
ERROR: Job failed: exit status 1