Clean up grant details feature flags and dead code

[ClaireValdivia]

Why is this issue important?

After grant details work is implemented for 2 weeks and is stable, we can remove the related feature flags. We also want to remove dead code from the previous implementation of grant details that is no longer relevant.

Implementation Plan

Feature flag definitions to remove:

• newGrantsDetailPageEnabled
  • remove from prod.tfvars, staging.tfvars, and sandbox.tfvars
  • remove from deploy-config.js and helpers/featureFlags/index.js

Dead code to remove:

• router/index.js: remove requiresNewGrantsDetailPageEnabled check
• GrantsTable.vue, Dashboard.vue, RecentActivity.vue, UpcomingCloseDates.vue: code to switch between legacy vs the new grant detail view
• GrantDetailsLegacy.vue: remove entirely

Relevant Code Snippets

No response

[jeffsmohan]

Does this issue include the task of cleaning up the related dead code? (Like the GrantDetailsLegacy modal?) Just wanted to make sure that's tracked somewhere.

[ClaireValdivia]

@jeffsmohan I think that would be great to include on this issue - would you be able to add in notes on which dead code to remove? Thank you!

[jeffsmohan]

✅ Updated implementation details to reflect the dead code to remove

[ClaireValdivia]

@TylerHendrickson just moved this to Ready as I noticed it has implementation details, but wondering if we should also add into this to remove the shareTerminologyEnabled feature flag to this as well?