Replace calls to Runnables.doNothing() with a do-nothing lambda, () -> {}.

`Runnables.doNothing()` exists only because Java lambdas didn't exist in 2013. `() -> {}` is shorter and more standard.

PiperOrigin-RevId: 974801764

Author: cpovirk

android/guava-tests/benchmark/com/google/common/util/concurrent/AbstractFutureFootprintBenchmark.java

@@ -83,7 +83,7 @@ public void run() {
       blockedThreads.add(thread);
     }
     for (int i = 0; i < numListeners; i++) {
-      f.addListener(Runnables.doNothing(), directExecutor());
+      f.addListener(() -> {}, directExecutor());
     }
     for (Thread thread : blockedThreads) {
       AbstractFutureBenchmarks.awaitWaiting(thread);

guava-tests/benchmark/com/google/common/util/concurrent/AbstractFutureFootprintBenchmark.java

@@ -83,7 +83,7 @@ public void run() {
       blockedThreads.add(thread);
     }
     for (int i = 0; i < numListeners; i++) {
-      f.addListener(Runnables.doNothing(), directExecutor());
+      f.addListener(() -> {}, directExecutor());
     }
     for (Thread thread : blockedThreads) {
       AbstractFutureBenchmarks.awaitWaiting(thread);