tox.ini: Take away GITHUB_ACTIONS from coveralls

.. so that it stops complaining about missing
variable GITHUB_TOKEN ..

> Running on Github Actions but GITHUB_TOKEN is not set.
> Add "env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}" to
> your step config.

(which may have write access) and that we stopped
sharing with coveralls in PR #97.

The related code checks for presence of variable
GITHUB_ACTIONS so we we take that variable
from coveralls-python.

Rather than excluding variable GITHUB_ACTIONS,
we include all other GITHUB_* variables used by
coveralls-python.  The list was derive like this:

$ git clone --depth 1 https://github.com/TheKevJames/coveralls-python
$ cd coveralls-python/
$ git grep -oh "GITHUB_[^ ':\`*]\+" | sort -u
GITHUB_ACTIONS
GITHUB_HEAD_REF
GITHUB_REF
GITHUB_REPOSITORY
GITHUB_RUN_ID
GITHUB_RUN_NUMBER
GITHUB_SHA
GITHUB_TOKEN

tox.ini

@@ -33,7 +33,14 @@ commands =
     coverage report -m
     bash -c 'set -x; [[ $\{GITHUB_ACTIONS:-false\} = false ]] || coveralls'
 setenv = {[base]setenv}
+# not GITHUB_ACTIONS!
 passenv =
     COVERALLS_REPO_TOKEN
-    GITHUB_*
+    GITHUB_HEAD_REF
+    GITHUB_REF
+    GITHUB_REPOSITORY
+    GITHUB_RUN_ID
+    GITHUB_RUN_NUMBER
+    GITHUB_SHA
+    GITHUB_TOKEN
 allowlist_externals = bash