ROX-31772: Fix Cypress selectors for nav and dashboard links

[sachaudh]

Description

This PR fixes the dashboard-related tests. Looks like I ended up checking the Vuln Mgmt, Config Mgmt, and Compliance Dashboard tests too. Those dashboards behave a bit oddly in v6 though, so I'll fix the UI errors when I get to those sections.

User-facing documentation

• CHANGELOG.md is updated OR update is not needed
• documentation PR is created and is linked above OR is not needed

Testing and quality

• the change is production ready: the change is GA, or otherwise the functionality is gated by a feature flag
• CI results are inspected

Automated testing

• added unit tests
• added e2e tests
• added regression tests
• added compatibility tests
• modified existing tests

How I validated my change

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

@@                 Coverage Diff                  @@
##             dv/ROX-28622-pf-6   #18022   +/-   ##
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  Coverage                     ?   49.35%           
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  Files                        ?     2699           
  Lines                        ?   198960           
  Branches                     ?        0           
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  Hits                         ?    98200           
  Misses                       ?    93143           
  Partials                     ?     7617           

Flag	Coverage Δ
go-unit-tests	49.35% <ø> (?)

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