replace custom last-successful action by inline curl job

[rhaas80]

Instead of using customized last-successful action, embed the required json parsing into action yaml file to reduce external dependencies:

curl -s https://api.github.com/repos/rhaas80/einsteintoolkit/actions/runs | jq 'first(.workflow_runs[] | select(.path==".github/workflows/docs.yml", .status=="success")) | .head_commit.id' | sed 's/\"//g'

gives the required last successful git hash.

This is basically the same as what the javascript in https://github.com/rhaas80/last-successful-commit-action/blob/master/dist/index.js does.

[rhaas80]

actually do this via a repository_dispatch action option. Something like in carpetx-tests: https://github.com/EinsteinToolkit/carpetx-tests/blob/7e95b32e5b558d125c288b3271193db7b19dcdfc/.github/workflows/CI.yml#L8 this will avoid confusion between this programmatic dispatch and a user's manual dispatch

[rhaas80]

EinsteinToolkit/tests#5