Extended Test Coverage for Dashboard and DRep directory

[NabinKawan]

List of changes

• Added test for dashboard learn more button action
• Added test for abstain and signal-no-confidence info button action
• Added test for DRep registration and edit dRep registration page restriction

Checklist

• related issue
• My changes generate no new warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the changelog
• I have added tests that prove my fix is effective or that my feature works

[mesudip]

Todo: Make the user story test numbering format consistent.

[mesudip]

LGTM