[helm]: make system integration enabled by default

Author: pkoutsovasilis

deploy/helm/elastic-agent/values.yaml

@@ -297,7 +297,7 @@ kubernetes:
 system:
   # -- enable System integration.
   # @section -- 4 - System integration
-  enabled: false
+  enabled: true
   # -- name of the output used in System integration. Note that this output needs to be defined in
   # [outputs](#1-outputs)
   # @section -- 4 - System integration