Remove beta label from searchable snapshot docs (#68724)

This feature will go GA in 7.11.

docs/reference/searchable-snapshots/apis/mount-snapshot.asciidoc

@@ -6,8 +6,6 @@
 <titleabbrev>Mount snapshot</titleabbrev>
 ++++
 
-beta::[]
-
 Mount a snapshot as a searchable snapshot index.
 
 [[searchable-snapshots-api-mount-request]]

docs/reference/searchable-snapshots/apis/searchable-snapshots-apis.asciidoc

@@ -3,8 +3,6 @@
 [[searchable-snapshots-apis]]
 == Searchable snapshots APIs
 
-beta::[]
-
 You can use the following APIs to perform searchable snapshots operations.
 
 * <<searchable-snapshots-api-mount-snapshot,Mount snapshot>>

docs/reference/searchable-snapshots/index.asciidoc

@@ -1,8 +1,6 @@
 [[searchable-snapshots]]
 == {search-snaps-cap}
 
-beta::[]
-
 {search-snaps-cap} let you reduce your operating costs by using
 <<snapshot-restore, snapshots>> for resiliency rather than maintaining
 <<scalability,replica shards>> within a cluster. When you mount an index from a