[20275] Set 2.11.x as EOL

[JesusPoderoso]

Description

This PR removes 2.11.x from supported versions in RELEASE_SUPPORT.md, from the backport command in the pull requests description template and from CI.

EDIT: Removed also CI's .repos and .meta files.

Contributor Checklist

• Commit messages follow the project guidelines.
• The code follows the style guidelines of this project.
• N/A Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• N/A Any new/modified methods have been properly documented using Doxygen.
• N/A Changes are ABI compatible.
• N/A Changes are API compatible.
• N/A New feature has been added to the versions.md file (if applicable).
• New feature has been documented/Current behavior is correctly described in the documentation.
  Related documentation PR: [20275] Set 2.11.x as EOL Fast-DDS-docs#663
• N/A Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

[MiguelCompany]

Note: If similar changes are required in the documentation repo, please link the corresponding PR in the description of this one

[JesusPoderoso]

@richiprosima please test this

[JesusPoderoso]

Note: If similar changes are required in the documentation repo, please link the corresponding PR in the description of this one

Applied here:

• [20275] Set 2.11.x as EOL Fast-DDS-docs#663