CI: activate github actions on 1.1.x (PR only)
same as #35459 against master. so should be OK when backported.
some failures not seen in other PRs. will re-run and see if they repeat.
```
=========================== short test summary info ============================
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_repr_deprecation_negative_int
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_repr_min_rows
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_str_max_colwidth
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_east_asian_unicode_false
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_east_asian_unicode_true
FAILED pandas/tests/io/formats/test_format.py::TestDataFrameFormatting::test_datetimelike_frame
= 6 failed, 73402 passed, 1017 skipped, 1051 xfailed, 240 warnings in 1450.34s (0:24:10) =
``` The option to re-run has disappeared from Travis again. currently bisecting an issue in dev env. will create an empty commit later/tomorrow. test failures unrelated Do we even need the branches option or can we just remove and have it run against any target? github actions updates the dev docs on the website. so only want that on master. @simonjayhawkins feel free to merge things like this when you need. @MeeseeksDev backport to 1.1.x