use bold instead of header

Author: TrentinTheKid

docs/developers/modules/beam.mdx

@@ -129,7 +129,7 @@ Custom colors can be created from any RGB values using `new Color(int red, int g
 
 <Tab>
 
-<h3>Displaying a Beam</h3>
+**Displaying a Beam**
 
 ```java
 public void displayBeamExample(Player viewer) {