Update write synchronisation comment

Co-authored-by: Ralf Jung <post@ralfj.de>

Author: tiif

src/shims/unix/linux/eventfd.rs

@@ -111,7 +111,7 @@ impl FileDescription for Event {
         // Else, block.
         match self.counter.checked_add(num) {
             Some(new_count @ 0..=MAX_COUNTER) => {
-                // Synchronize with all prior `write` calls to this FD.
+                // Future `read` calls will synchronize with this write, so update the FD clock.
                 if let Some(clock) = &ecx.release_clock() {
                     self.clock.join(clock);
                 }