Remove outdated message in Tag page

What does this MR do and why?

In a Tag's "show" page:

• the description of the associated Release is displayed, if the said description exists

  

• a This tag has no release notes message is displayed if the associated Release has no description

  

We believe this is outdated UI/UX from a time when we didn't have the concept of "Release" as a first-class entity. Now, the Tag page has list of links to Release pages (see #342820 (comment 807783974) & #267558 (closed)), so we don't have to display the Release notes (or lack thereof) in the Tag page.

For further details, see: #383594 (closed)

Screenshots or screen recordings

As shown below, whether the Tag's associated Release has a description or not, the Release note or the This tag has no release notes are not displayed on the Tag's page

A Tag where the associated Release has a note

A Tag where the associated Release DOES NOT have a note

How to set up and validate locally

Setup

In an example project, navigate to Deployments -> Releases and create:

• a Release with an associated Tag; the Release must have a description

  

• a Release with an associated Tag; DO NOT fill in a description for the Release

  

Validation

1. Navigate to the project's Tags page (i.e.: <your-project-url>/-/tags)
2. Click on each Tag
3. Verify that each Tag does not have the Release note or the This tag has no release notes message displayed.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Review tracking

• frontend - ✅
• backend - ✅
• QA - ✅
• test - ✅