[Fleet] Remove No Tags from add/remove popover

[Supplementing]

Closes #218636

Summary

• Removes the No Tags option from the add/remove popover as it is not actually a tag, but only to be used in the filter dropdown.

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

Identify risks

N/A

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[Supplementing]

@elasticmachine merge upstream

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 737eaf1

Failed CI Steps

• Jest Tests #1
• Fleet Cypress Tests #1

Test Failures

• [job] [logs] Jest Tests #1 / discover responsive sidebar should render buttons in data view picker correctly
• [job] [logs] Fleet Cypress Tests #1 / View agents list Agent status filter should filter on healthy and unhealthy
• [job] [logs] Fleet Cypress Tests #1 / View agents list Bulk actions should allow to bulk upgrade agents and cancel that upgrade

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
fleet	1.7MB	1.7MB	+100.0B