Fix wrong docs on Job.join (#2616)

* Fix wrong docs on Job.join and Job.cancelAndJoin

Fixes #2615

Author: elizarov

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

@@ -252,9 +252,9 @@ public interface Job : CoroutineContext.Element {
      * suspending function is invoked or while it is suspended, this function
      * throws [CancellationException].
      *
-     * In particular, it means that a parent coroutine invoking `join` on a child coroutine that was started using
-     * `launch(coroutineContext) { ... }` builder throws [CancellationException] if the child
-     * had crashed, unless a non-standard [CoroutineExceptionHandler] is installed in the context.
+     * In particular, it means that a parent coroutine invoking `join` on a child coroutine throws
+     * [CancellationException] if the child had failed, since a failure of a child coroutine cancels parent by default,
+     * unless the child was launched from within [supervisorScope].
      *
      * This function can be used in [select] invocation with [onJoin] clause.
      * Use [isCompleted] to check for a completion of this job without waiting.
@@ -498,9 +498,9 @@ internal fun Job.disposeOnCompletion(handle: DisposableHandle): DisposableHandle
  * suspending function is invoked or while it is suspended, this function
  * throws [CancellationException].
  *
- * In particular, it means that a parent coroutine invoking `cancelAndJoin` on a child coroutine that was started using
- * `launch(coroutineContext) { ... }` builder throws [CancellationException] if the child
- * had crashed, unless a non-standard [CoroutineExceptionHandler] is installed in the context.
+ * In particular, it means that a parent coroutine invoking `cancelAndJoin` on a child coroutine throws
+ * [CancellationException] if the child had failed, since a failure of a child coroutine cancels parent by default,
+ * unless the child was launched from within [supervisorScope].
  *
  * This is a shortcut for the invocation of [cancel][Job.cancel] followed by [join][Job.join].
  */