Remove EventLoopError::AlreadyRunning

This is already prevented by the type-system, and as such it doesn't
make sense to have an error case for this.

src/platform_impl/windows/event_loop/runner.rs

@@ -143,10 +143,6 @@ impl<T> EventLoopRunner<T> {
         }
     }
 
-    pub fn state(&self) -> RunnerState {
-        self.runner_state.get()
-    }
-
     pub fn set_control_flow(&self, control_flow: ControlFlow) {
         self.control_flow.set(control_flow)
     }