changelog: add 8.15.1 entry (#13966) (#13967)

Signed-off-by: inge4pres <francesco.gualazzi@elastic.co>
(cherry picked from commit 67734bd)

Co-authored-by: Francesco Gualazzi <inge4pres@users.noreply.github.com>

changelogs/8.15.asciidoc

@@ -1,7 +1,32 @@
 [[apm-release-notes-8.15]]
 == APM version 8.15
+
+* <<apm-release-notes-8.15.1>>
 * <<apm-release-notes-8.15.0>>
 
+[float]
+[[apm-release-notes-8.15.1]]
+=== APM version 8.15.1
+
+https://github.com/elastic/apm-server/compare/v8.15.0\...v8.15.1[View commits]
+
+[float]
+==== Bug fixes
+
+- Fix fallback memory limit check conversion from Bytes to Gigabytes {pull}13838[13838]
+
+[float]
+==== Breaking Changes
+
+[float]
+==== Deprecations
+
+[float]
+==== Intake API Changes
+
+[float]
+==== Added
+
 [float]
 [[apm-release-notes-8.15.0]]
 === APM version 8.15.0