Modify the KDoc for awaitAll (Kotlin#3187)

It seems like there is an extra "when" and a missing "for".

Author: b0ri5

kotlinx-coroutines-core/common/src/Await.kt

@@ -29,8 +29,8 @@ public suspend fun <T> awaitAll(vararg deferreds: Deferred<T>): List<T> =
  * when all deferred computations are complete or resumes with the first thrown exception if any of computations
  * complete exceptionally including cancellation.
  *
- * This function is **not** equivalent to `this.map { it.await() }` which fails only when when it sequentially
- * gets to wait the failing deferred, while this `awaitAll` fails immediately as soon as any of the deferreds fail.
+ * This function is **not** equivalent to `this.map { it.await() }` which fails only when it sequentially
+ * gets to wait for the failing deferred, while this `awaitAll` fails immediately as soon as any of the deferreds fail.
  *
  * This suspending function is cancellable.
  * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting,