Backport of chor: remove temporary CONSUL_HCP_LINK_ENABLED env flag into release/1.18.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #20552 to be assessed for backporting due to the inclusion of the label backport/1.18.

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The person who merged in the original PR is:
@valeriia-ruban
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

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The below text is copied from the body of the original PR.

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Description

Remove temporary CONSUL_HCP_LINK_ENABLED env flag.
PR it was added: #20392

Testing & Reproduction steps

1. go to consul
2. go to Service list - link to HCP banner is visible
3. set CONSUL_HCP_LINK_ENABLED to true and then to false (from cookies or with running locally Scenario('CONSUL_HCP_LINK_ENABLED=true')) - banner is still there for any value

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• ddabb40

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[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR

[valeriia-ruban]

manually backported in #20577