Update 2.5.x continuous integration workflow

[guillermocalvo]

@puneetbehl I made the workflow publish snapshot artifacts independently to s01.oss.sonatype.org and repo.grails.org because the latter keeps failing randomly every now and then with Internal Server Error:

Execution failed for task ':grails-plugin-filters:uploadPublished'.
> Could not publish configuration 'published'
   > Failed to deploy metadata:
     Could not transfer metadata org.grails:grails-plugin-filters/maven-metadata.xml
     from/to remote (https://repo.grails.org/grails/libs-snapshots-local):
       Failed to transfer file:
       https://repo.grails.org/grails/libs-snapshots-local/org/grails/grails-plugin-filters/maven-metadata.xml.
       Return code is: 500, ReasonPhrase: Internal Server Error.