removed theta from docs

docs/network/physics.html

@@ -91,8 +91,7 @@ var options = {
       avoidOverlap: 0
     },
     forceAtlas2Based: {
-      theta: 0.5,
-      gravitationalConstant: -800,
+      gravitationalConstant: -50,
       centralGravity: 0.01,
       springConstant: 0.08,
       springLength: 100,