[gitlab-ci] only trigger readthedocs on branch/default

7 jobs for branch/default in 2 minutes and 10 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Tests
passed black #29799

00:01:19

passed check-manifest #29798

00:01:07

passed flake8 #29797

00:01:16

passed mypy #29800

00:01:32

passed py3 #29796

00:01:24

 
  After Tests
passed trigger-other-pipelines #29801

00:00:37

passed trigger-readthedocs #29802

00:00:35