Set explicit clear alpha for documentation scenes (#9582)

* Explicit clear alpha

* Explicit clear alpha

* Explicit clear alpha

docs/scenes/bones-browser.html

@@ -59,7 +59,7 @@
 				renderer = new THREE.WebGLRenderer( { antialias: true } );
 				renderer.setPixelRatio( window.devicePixelRatio );
 				renderer.setSize( window.innerWidth, window.innerHeight );
-				renderer.setClearColor( 0x000000 );
+				renderer.setClearColor( 0x000000, 1 );
 				document.body.appendChild( renderer.domElement );
 
 				orbit = new THREE.OrbitControls( camera, renderer.domElement );

docs/scenes/geometry-browser.html

@@ -52,7 +52,7 @@
 			var renderer = new THREE.WebGLRenderer( { antialias: true } );
 			renderer.setPixelRatio( window.devicePixelRatio );
 			renderer.setSize( window.innerWidth, window.innerHeight );
-			renderer.setClearColor( 0x000000 );
+			renderer.setClearColor( 0x000000, 1 );
 			document.body.appendChild( renderer.domElement );
 
 			var orbit = new THREE.OrbitControls( camera, renderer.domElement );

docs/scenes/material-browser.html

@@ -50,7 +50,7 @@
 			var renderer = new THREE.WebGLRenderer( { antialias: true } );
 			renderer.setPixelRatio( window.devicePixelRatio );
 			renderer.setSize( window.innerWidth, window.innerHeight );
-			renderer.setClearColor( 0x000000 );
+			renderer.setClearColor( 0x000000, 1 );
 			document.body.appendChild( renderer.domElement );
 
 			var ambientLight = new THREE.AmbientLight( 0x000000 );