Remove titlestr and titlecomponent from replaceSectionActionItem and replaceActionItem methods in course/amd/src/actions.js

In MDL-64819 the titlestr and titlecomponent from replaceSectionActionItem and replaceActionItem methods in course/amd/src/actions.js are not used anymore. For now, a comment has been added to the replaceActionItem jsdoc, but some deprecation process should be raised for them to make sure the legacy code is cleaned at some point.