DOC-13223 sizing guidelines, note on residentRatio (#347)

* DOC-13223: rebased to 7.6

* DOC-13223: changed to note

* Update index-partitioning.adoc

Author: TimLFletcher

modules/n1ql/pages/n1ql-language-reference/index-partitioning.adoc

@@ -532,6 +532,8 @@ Non-array fields will be ignored.
 | `50`
 |===
 
+NOTE: Couchbase recommends setting the residentRatio property value over 10 to avoid issues, for example, index build failures.
+
 To provide sizing estimation, you can use a command similar to the following examples.
 
 [.server]