fix for navmesh (re)baking issue

fix for navmesh (re)baking issues in demo
- changed level mesh size/scale (was way to small to be useable)
- changed navmesh agent settings (default radius to large, slope values to small)

3d/navmesh/navmesh.gd

@@ -1,6 +1,6 @@
 extends Navigation
 
-const SPEED = 4.0
+const SPEED = 10.0
 
 var camrot = 0.0