Fix incorrect waker update condition (#7656)

This bug was first found and partially fixed by @VolodymyrBg in #7317 - this PR applies the same fix everywhere else.

The old logic updated the waker when it already matched the context, and did nothing when it was stale:

```rust
if waker.will_wake(cx.waker()) {
self.waker = Some(cx.waker().clone());
}
```

This is the wrong way around. We only want to update the waker if it doesn't match the current context:

```rust
if !waker.will_wake(cx.waker()) {
self.waker = Some(cx.waker().clone());
}
```

I don't think we've ever noticed any issues, but it’s a subtle bug that could lead to missed wakeups.

beacon_node/lighthouse_network/src/rpc/handler.rs

@@ -377,7 +377,7 @@ where
         ConnectionHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::ToBehaviour>,
     > {
         if let Some(waker) = &self.waker {
-            if waker.will_wake(cx.waker()) {
+            if !waker.will_wake(cx.waker()) {
                 self.waker = Some(cx.waker().clone());
             }
         } else {