docs: Fix SQL queries in realtime documentation (supabase#41519)

I'm relatively new to supabase, but in my current understanding the SQL
selects are inconsistent with the given example schema as the column is
named `room_topic` there.

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

Yes.

## What kind of change does this PR introduce?

Updates documentation.


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-->

## Summary by CodeRabbit

## Release Notes

* **Documentation**
* Corrected authorization policy examples in realtime guides to use
accurate column references for topic-based access control in Broadcast
and Presence features.

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settings.</sub>

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Co-authored-by: Chris Chinchilla <chris.ward@supabase.io>

Author: thammerl

apps/docs/content/guides/realtime/authorization.mdx

@@ -133,7 +133,7 @@ exists (
       rooms_users
     where
       user_id = (select auth.uid())
-      and topic = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('broadcast')
   )
 );
@@ -266,7 +266,7 @@ with check (
       rooms_users
     where
       user_id = (select auth.uid())
-      and topic = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('broadcast')
   )
 );
@@ -293,7 +293,7 @@ using (
       rooms_users
     where
       user_id = (select auth.uid())
-      and topic = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('presence')
   )
 );
@@ -316,7 +316,7 @@ with check (
       rooms_users
     where
       user_id = (select auth.uid())
-      and name = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('presence')
   )
 );
@@ -343,7 +343,7 @@ using (
       rooms_users
     where
       user_id = (select auth.uid())
-      and topic = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('broadcast', 'presence')
   )
 );
@@ -366,7 +366,7 @@ with check (
       rooms_users
     where
       user_id = (select auth.uid())
-      and name = (select realtime.topic())
+      and room_topic = (select realtime.topic())
       and realtime.messages.extension in ('broadcast', 'presence')
   )
 );