Remove security warning from 00500-schedule-tables.md (#4463)

Now that scheduled reducers are private, this warning is no longer
necessary.

# Description of Changes

- removed Security Considerations section from Schedule Tables
documentation

Signed-off-by: Tao Tien <29749622+taotien@users.noreply.github.com>
Co-authored-by: joshua-spacetime <josh@clockworklabs.io>

Author: taotien

docs/docs/00200-core-concepts/00300-tables/00500-schedule-tables.md

@@ -364,77 +364,6 @@ ctx.db[reminder].insert(Reminder{
 3. **When the time arrives**, the specified reducer/procedure is automatically called with the row as a parameter
 4. **The row is typically deleted** or updated by the reducer after processing
 
-## Security Considerations
-
-:::warning Scheduled Reducers Are Callable by Clients
-Scheduled reducers are normal reducers that can also be invoked by external clients. If a scheduled reducer should only execute via the scheduler, add authentication checks.
-:::
-
-<Tabs groupId="server-language" queryString>
-<TabItem value="typescript" label="TypeScript">
-
-```typescript
-export const send_reminder = spacetimedb.reducer({ arg: Reminder.rowType }, (ctx, { arg }) => {
-  if (!ctx.senderAuth.isInternal) {
-    throw new SenderError('This reducer can only be called by the scheduler');
-  }
-  // Process the scheduled reminder
-});
-```
-
-</TabItem>
-<TabItem value="csharp" label="C#">
-
-```csharp
-using SpacetimeDB;
-
-public static partial class Module
-{
-    [SpacetimeDB.Reducer]
-    public static void SendReminder(ReducerContext ctx, Reminder reminder)
-    {
-        if (!ctx.SenderAuth.IsInternal)
-        {
-            throw new Exception("This reducer can only be called by the scheduler");
-        }
-        // Process the scheduled reminder
-    }
-}
-```
-
-</TabItem>
-<TabItem value="rust" label="Rust">
-
-```rust
-#[spacetimedb::reducer]
-fn send_reminder(ctx: &ReducerContext, reminder: Reminder) -> Result<(), String> {
-    if !ctx.sender_auth().is_internal() {
-        return Err("This reducer can only be called by the scheduler".to_string());
-    }
-    // Process the scheduled reminder
-    Ok(())
-}
-```
-
-</TabItem>
-<TabItem value="cpp" label="C++">
-
-```cpp
-SPACETIMEDB_REDUCER(send_reminder, ReducerContext ctx, Reminder arg)
-{
-    // Check if this reducer is being called by the scheduler (internal)
-    if (!ctx.sender_auth().is_internal()) {
-        return Err("This reducer can only be called by the scheduler");
-    }
-    
-    // Process the scheduled reminder
-    return Ok();
-}
-```
-
-</TabItem>
-</Tabs>
-
 ## Use Cases
 
 - **Reminders and notifications** - Schedule messages to be sent at specific times