Add deprecation warning to Jaeger API docs (#4761) (#4771)

* add deprecation warning to Jaeger API docs

* leverage warning header in asciidoc

* update pull request link

* minor lang correction

(cherry picked from commit b8f4f23)

Co-authored-by: Ruben van Staden <[email protected]>

Author: mergify[bot]

docs/en/observability/apm/api/apm-server/api-jaeger.asciidoc

@@ -1,6 +1,11 @@
 [[apm-api-jaeger]]
 = Jaeger event intake
 
+[WARNING]
+====
+- Support for Jaeger is deprecated, and will be removed in a future release https://github.com/elastic/apm-server/issues/11671[#1167]
+====
+
 Elastic APM natively supports Jaeger, an open-source, distributed tracing system.
 <<apm-jaeger-integration,Learn more>>.