Fix Bug With Uppercase Radio Keys (#32997) (master) (#33031)

Co-authored-by: Thomas <87614336+Aeshus@users.noreply.github.com>

Content.Shared/Chat/SharedChatSystem.cs

@@ -106,7 +106,7 @@ public abstract class SharedChatSystem : EntitySystem
         if (!(input.StartsWith(RadioChannelPrefix) || input.StartsWith(RadioChannelAltPrefix)))
             return;
 
-        if (!_keyCodes.TryGetValue(input[1], out _))
+        if (!_keyCodes.TryGetValue(char.ToLower(input[1]), out _))
             return;
 
         prefix = input[..2];