Document change to size > 0 setting for request cache (#8684)

* document change to size > 0 setting

Signed-off-by: Peter Alfonsi <petealft@amazon.com>

* Update _search-plugins/caching/request-cache.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Peter Alfonsi <peter.alfonsi@gmail.com>

* Update _search-plugins/caching/request-cache.md

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

---------

Signed-off-by: Peter Alfonsi <petealft@amazon.com>
Signed-off-by: Peter Alfonsi <peter.alfonsi@gmail.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Peter Alfonsi <petealft@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Nathan Bower <nbower@amazon.com>

Author: 4 people

_search-plugins/caching/request-cache.md

@@ -28,6 +28,7 @@ Setting | Data type  | Default | Level | Static/Dynamic | Description
 `indices.cache.cleanup_interval` | Time unit  | `1m` (1 minute)  | Cluster | Static | Schedules a recurring background task that cleans up expired entries from the cache at the specified interval. 
 `indices.requests.cache.size` | Percentage | `1%`      | Cluster | Static | The cache size as a percentage of the heap size (for example, to use 1% of the heap, specify `1%`). 
 `index.requests.cache.enable` | Boolean    | `true`    | Index | Dynamic | Enables or disables the request cache. 
+`indices.requests.cache.maximum_cacheable_size` | Integer    | `0`    | Cluster | Dynamic | Sets the maximum `size` of queries to be added to the request cache.
 
 ### Example