docs: update redis cache client options (#10521)

Between v3 and v4 in node-redis the client options changed for a collection of socket related
paramaters. In the caching documentation the v3 format for used for `host` and `socket`. When
following the documented example the redis client would default to `localhost` even when a
different value for `host` was specified.

Closes: #9987

docs/caching.md

@@ -137,8 +137,10 @@ Example:
     cache: {
         type: "redis",
         options: {
-            host: "localhost",
-            port: 6379
+            socket: {
+                host: "localhost",
+                port: 6379
+            }
         }
     }
 }
@@ -240,8 +242,10 @@ Example:
     cache: {
         type: "redis",
         options: {
-            host: "localhost",
-            port: 6379
+            socket: {
+                host: "localhost",
+                port: 6379
+            }
         },
         ignoreErrors: true
     }