This is a reland of fdbb5beb

Original change's description:
> [turbofan] Remove obsolete fast-path
> 
> This is subsumed by an optimization is JSCallReducer now.
> 
> Bug: v8:7340, v8:7250
> Change-Id: I6c706177e410abd57ea24a7ffbbe2437733ed7c7
> Reviewed-on: https://chromium-review.googlesource.com/946088
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51697}

Bug: v8:7340, v8:7250
Change-Id: Ic370c82af78ab8916608f8d774ef1b50d99b894e
Reviewed-on: https://chromium-review.googlesource.com/946010Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51705}