Revert "DevTools: fixed scheduleStepInto for Node 8.x"

This reverts commit 99590e1f.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> DevTools: fixed scheduleStepInto for Node 8.x
> 
> Node 8.x does not support breakOnAsyncCall param of
> Debugger.stepInto method.
> 
> R=​dgozman@chromium.org
> 
> Bug: none
> Change-Id: I0e59e0a3742b85a2fd466ac1bac5f7b75aa7f841
> Reviewed-on: https://chromium-review.googlesource.com/c/1352533
> Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
> Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#612075}

TBR=dgozman@chromium.org,kozyatinskiy@chromium.org

Change-Id: Id375af68281dd1316f907f2ea0ee9cfd07b3390e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://chromium-review.googlesource.com/c/1356126Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612449}

third_party/blink/renderer/devtools/front_end/sdk/DebuggerModel.js

@@ -228,9 +228,6 @@ SDK.DebuggerModel = class extends SDK.SDKModel {
   }
 
   scheduleStepIntoAsync() {
-    // Node v8.x does not support breakOnAsyncCall flag but supports old style schdeuleStepIntoAsync.
-    // End-of-life of Node 8.x is around December 2019.
-    this._agent.scheduleStepIntoAsync();
     this._agent.invoke_stepInto({breakOnAsyncCall: true});
   }