Update the "Go" devfile test for testing the "go to definition" function

Currently for testing the "go to definition" function, the "Go" devfile test tries to use this function for the "string" object. But "go to definition" function shouldn't work for the "string" object (explained here https://issues.redhat.com/browse/CRW-1019?focusedCommentId=14400900&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14400900).

We should found an object for use the "go to definition" function and rework the "Go" devfile for working with it.