Update method-syntax.md

Fix wrong radius valve from 0.0 to 1.0 as above

src/doc/trpl/method-syntax.md

@@ -188,7 +188,7 @@ struct CircleBuilder {
 
 impl CircleBuilder {
     fn new() -> CircleBuilder {
-        CircleBuilder { x: 0.0, y: 0.0, radius: 0.0, }
+        CircleBuilder { x: 0.0, y: 0.0, radius: 1.0, }
     }
 
     fn x(&mut self, coordinate: f64) -> &mut CircleBuilder {