[DOCS] Use attribute in snapshot index compatibility

docs/reference/snapshot-restore/index.asciidoc

@@ -149,8 +149,9 @@ 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 8.0 cluster, the restore attempt will
-fail. Keep this in mind if you take a snapshot before upgrading a cluster.
+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