Fix rc_room_creation and rc_reports docs - remove per_user typo (#18998)

Author: spaetz

changelog.d/18998.doc

@@ -0,0 +1 @@
+Fix documentation for `rc_room_creation` and `rc_reports` to clarify that a `per_user` rate limit is not supported.

docs/usage/configuration/config_documentation.md

@@ -2006,9 +2006,8 @@ This setting has the following sub-options:
 Default configuration:
 ```yaml
 rc_reports:
-  per_user:
-    per_second: 1.0
-    burst_count: 5.0
+  per_second: 1.0
+  burst_count: 5.0
 ```
 
 Example configuration:
@@ -2031,9 +2030,8 @@ This setting has the following sub-options:
 Default configuration:
 ```yaml
 rc_room_creation:
-  per_user:
-    per_second: 0.016
-    burst_count: 10.0
+  per_second: 0.016
+  burst_count: 10.0
 ```
 
 Example configuration:

schema/synapse-config.schema.yaml

@@ -2259,9 +2259,8 @@ properties:
       Setting this to a high value allows users to report content quickly, possibly in
       duplicate. This can result in higher database usage.
     default:
-      per_user:
-        per_second: 1.0
-        burst_count: 5.0
+      per_second: 1.0
+      burst_count: 5.0
     examples:
       - per_second: 2.0
         burst_count: 20.0
@@ -2270,9 +2269,8 @@ properties:
     description: >-
       Sets rate limits for how often users are able to create rooms.
     default:
-      per_user:
-        per_second: 0.016
-        burst_count: 10.0
+      per_second: 0.016
+      burst_count: 10.0
     examples:
       - per_second: 1.0
         burst_count: 5.0