Change CI doc builds to upload artifacts even when the build fails

[vyasr]

Sphinx builds often fail in non-fatal ways. For example, the documentation may be produced with rendering issues. Diagnosing these issues in CI can be challenging because the produced documentation is not currently published unless the build succeeds. We should modify the doc build jobs to upload the documentation even if the build fails to make debugging easier. This can be done by adding set +e before the make html/sphinx-build invocation, saving the exit code, and triggering the upload before returning the resulting exit code.