Fix `get_test_texture()` returning an almost fully white texture

The texture's appearance is now similar to the texture that was displayed
on the TestCube node in Godot 2.x.

servers/rendering_server.cpp

@@ -140,9 +140,9 @@ RID RenderingServer::get_test_texture() {
 					c.b = y;
 				}
 
-				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 0] = uint8_t(CLAMP(c.r * 255, 0, 255));
-				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 1] = uint8_t(CLAMP(c.g * 255, 0, 255));
-				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 2] = uint8_t(CLAMP(c.b * 255, 0, 255));
+				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 0] = uint8_t(CLAMP(c.r, 0, 255));
+				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 1] = uint8_t(CLAMP(c.g, 0, 255));
+				w[(y * TEST_TEXTURE_SIZE + x) * 3 + 2] = uint8_t(CLAMP(c.b, 0, 255));
 			}
 		}
 	}