fix clippy needless lifetimes (#769)

+ ignore them for bevy where we often want explicitness

src_testbed/testbed.rs

@@ -469,7 +469,7 @@ impl TestbedApp {
     }
 }
 
-impl<'a, 'b, 'c, 'd, 'e, 'f> TestbedGraphics<'a, 'b, 'c, 'd, 'e, 'f> {
+impl TestbedGraphics<'_, '_, '_, '_, '_, '_> {
     pub fn set_body_color(&mut self, body: RigidBodyHandle, color: [f32; 3]) {
         self.graphics.set_body_color(self.materials, body, color);
     }
@@ -526,7 +526,7 @@ impl<'a, 'b, 'c, 'd, 'e, 'f> TestbedGraphics<'a, 'b, 'c, 'd, 'e, 'f> {
     }
 }
 
-impl<'a, 'b, 'c, 'd, 'e, 'f> Testbed<'a, 'b, 'c, 'd, 'e, 'f> {
+impl Testbed<'_, '_, '_, '_, '_, '_> {
     pub fn set_number_of_steps_per_frame(&mut self, nsteps: usize) {
         self.state.nsteps = nsteps
     }