apm: change tail_sampling_storage_limit config default to 0GB (#12543)

sampling.tail.storage_limit is 0 by default in 9.0. See elastic/apm-server#15467 .
As UI validation requires unit (e.g. GB), set apm integration default storage limit to 0GB which carries the same meaning.

packages/apm/changelog.yml

@@ -1,3 +1,8 @@
+- version: 9.0.0-preview-1738343125
+  changes:
+    - description: Change default sampling.tail.storage_limit config to 0GB
+      type: breaking-change
+      link: https://github.com/elastic/integrations/pull/12543
 - version: 8.15.0-preview-1716438434
   changes:
     - description: Remove data streams from integration package

packages/apm/manifest.yml

@@ -1,7 +1,7 @@
 format_version: 3.1.0
 name: apm
 title: Elastic APM
-version: 8.15.0-preview-1716438434
+version: 9.0.0-preview-1738343125
 description: Monitor, detect, and diagnose complex application performance issues.
 type: integration
 categories: ["elastic_stack", "monitoring"]
@@ -10,7 +10,7 @@ conditions:
     capabilities:
       - apm
   kibana:
-    version: ^8.15.0
+    version: ^9.0.0
 icons:
   - src: /img/logo_apm.svg
     title: APM Logo
@@ -171,7 +171,7 @@ policy_templates:
             default: false
           - name: tail_sampling_storage_limit
             type: text
-            default: "3GB"
+            default: "0GB"
         template_path: template.yml.hbs
 owner:
   type: elastic