ci: change capitalization of secret

[line-o]

refs #16

No luck so far. neither capitalisation nor token expiry seem to be the problem.

-- update --

It seems to be a mixture of issues as with a different token and on release (eXist v6.2.0) it is obvious that the environment variable is available inside the docker container.

[line-o]

As discussed with @duncdrum in order to get CI in a functional state we need

1. a non-expired PAT created from the organization that is available as a secret to the test workflow (node.js.yml)
   that replaces the current one
2. to test with a different docker image for 5.3.0, if that will build or update the test matrix to run on latest 5.x.x (which is 5.5.1 at the moment)
3. mark the test on latest exist-db as experimental and allow it to fail

[line-o]

Maybe adapting roaster's workflow would be and advantage

[duncdrum]

see #22