Update container registry removal success notification

What does this MR do?

This MR changes the copy of the successful image notification notice and adds an unit test to verify that the copy now contains the repository / image name

Screenshots

How to test

To test this work is necessary to have the container registry up and running, at least an image with a tag pushed and delete them. Since this is quite a good amount of work to test a simple copy change I am happy to help anyone really interested in checking this.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Part of #55275 (closed)