Revert of [es6] support AssignmentPattern as LHS in for-in/of loops (patchset #9 id:280001 of https://codereview.chromium.org/1508933004/ )

Reason for revert:
Hits unreachable code (found by fuzzer). Example crasher:

"for(();;);"

Original issue's description:
> [es6] support AssignmentPattern as LHS in for-in/of loops
>
> BUG=v8:811, v8:4599
> LOG=N
> R=adamk@chromium.org, rossberg@chromium.org
>
> Committed: https://crrev.com/e47bdb775564b2cd8365047425898ab4274190a6
> Cr-Commit-Position: refs/heads/master@{#32773}

TBR=rossberg@chromium.org,caitpotter88@gmail.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:811, v8:4599

Review URL: https://codereview.chromium.org/1511773009

Cr-Commit-Position: refs/heads/master@{#32774}