[DOCS] Swap 7.16 for `{prev-major-last}` var (#82616)

docs/reference/snapshot-restore/index.asciidoc

@@ -148,10 +148,10 @@ You can't restore an index to an earlier version of {es}. For example, you can't
 restore an index created in 7.6.0 to a cluster running 7.5.0.
 
 A compatible snapshot can contain indices created in an incompatible version.
-For example, a snapshot of a 7.16 cluster can contain an index created in 6.8.
-If you try to restore the 6.8 index to an {minor-version} cluster, the restore
-attempt will fail. Keep this in mind if you take a snapshot before upgrading a
-cluster.
+For example, a snapshot of a {prev-major-last} cluster can contain an index
+created in 6.8. If you try to restore the 6.8 index to an {minor-version}
+cluster, the restore attempt will fail. Keep this in mind if you take a snapshot
+before upgrading a cluster.
 
 As a workaround, you can first restore the index to another cluster running the
 latest version of {es} that's compatible with both the index and your current