update language around eliminating replica shards (#90369)

Replica shards required to avoid data loss during indexing.  Therefore IMHO the language should be changed

 from 
Searchable snapshots eliminate the need for replica shards 
to
Searchable snapshots eliminate the need for replica shards after rollover from hot

docs/reference/searchable-snapshots/index.asciidoc

@@ -6,8 +6,8 @@ infrequently accessed and read-only data in a very cost-effective fashion. The
 <<cold-tier,cold>> and <<frozen-tier,frozen>> data tiers use {search-snaps} to
 reduce your storage and operating costs.
 
-{search-snaps-cap} eliminate the need for <<scalability,replica shards>>,
-potentially halving the local storage needed to search your data.
+{search-snaps-cap} eliminate the need for <<scalability,replica shards>>
+after rollover from hot, potentially halving the local storage needed to search your data.
 {search-snaps-cap} rely on the same snapshot mechanism you already use for
 backups and have minimal impact on your snapshot repository storage costs.