add release notes for 8.11.2 (#12174)

Author: colleenmcginnis

Diff for: changelogs/8.11.asciidoc

@@ -3,9 +3,18 @@
 
 https://github.com/elastic/apm-server/compare/8.10\...8.11[View commits]
 
+* <<release-notes-8.11.2>>
 * <<release-notes-8.11.1>>
 * <<release-notes-8.11.0>>
 
+[float]
+[[release-notes-8.11.2]]
+=== APM version 8.11.2
+
+https://github.com/elastic/apm-server/compare/v8.11.1\...v8.11.2[View commits]
+
+No significant changes.
+
 [float]
 [[release-notes-8.11.1]]
 === APM version 8.11.1