docs: fix typo

Author: xchopin

docs/administrator/mongo_indices.md

@@ -7,7 +7,7 @@
 
 
 
-| :warning:   | For the fastest processing, ensure that your indexes fit entirely in RAM so that the system can avoid reading the index from disk. |
+| :warning:   | For the fastest processing, ensure that your indices fit entirely in RAM so that the system can avoid reading the index from disk. |
 |:----:|:----|
 
 ## Why indexing my collections?