Add automated test for "Delete Annotation"

The manual test is here: Delete Annotation

Existing automated coverage

• AnnotationsIT#addEditAndDeleteAnnotations: Step 1 (adds annotations with CTRL+M in view mode) and asserts the Comments tab shows a Delete button for each annotation; deletion is done through the annotation bubble, not the Comments tab, and the test never asserts the annotation is gone
• InplaceEditWithAnnotationsIT#editInplaceWithAnnotations: Steps 2-4 and the expected result (Comments tab trash icon + confirm, annotation count drops) but only while the page is in in-place edit mode and on annotations created through REST

Missing automated coverage

• In view mode, add an annotation with CTRL+M (AnnotatableViewPage#addAnnotation)
• Open the Comments tab and delete the annotation comment with the trash icon + 'Delete' confirmation (CommentsTab#deleteCommentByID)
• Assert the comment is no longer listed in the Comments tab
• Reload the page with annotations shown and assert the annotation highlight is gone (getAnnotationCount decreased, no highlight for the annotated text)
• Also assert the annotation is gone after the existing bubble deletions in addEditAndDeleteAnnotations

Suggested location: xwiki-platform-core/xwiki-platform-annotation/xwiki-platform-annotation-test/xwiki-platform-annotation-test-docker/src/test/it/org/xwiki/annotation/test/ui/AnnotationsIT.java

Found by comparing the XWiki 18.4.4 manual test runs against the automated tests on master (a0055f10a1a).