[DOCS] Add xrefs to rollup overview (#68119)

docs/reference/glossary.asciidoc

@@ -453,6 +453,7 @@ ifdef::permanently-unreleased-branch[]
 // tag::rollup-def[]
 Aggregates an index's time series data and stores the results in a new read-only
 index. For example, you can roll up hourly data into daily or weekly summaries.
+See {ref}/xpack-rollup.html[Roll up your data].
 // end::rollup-def[]
 
 endif::[]

docs/reference/rollup/apis/put-job.asciidoc

@@ -11,8 +11,8 @@ ifdef::permanently-unreleased-branch[]
 
 // tag::legacy-rollup-admon[]
 WARNING: This documentation is about legacy rollups. Legacy rollups are
-deprecated and will be replaced by new rollup functionality introduced in {es}
-7.x.
+deprecated and will be replaced by <<xpack-rollup,new rollup functionality>>
+introduced in {es} 7.x.
 // end::legacy-rollup-admon[]
 
 Creates a legacy {rollup-job}.