Revert of Fix an OOB read through CallSite.GetFunctionName (patchset #1 id:1 of https://codereview.chromium.org/2199333002/ )

Reason for revert:
We can revert this now that it's landed on 5.3.

Original issue's description:
> Fix an OOB read through CallSite.GetFunctionName
>
> The func_index parameter passed to GetWasmFunctionNameFromTable can be
> user-controlled through the CallSite constructor. Catch out-of-bounds
> reads and return null as the function name in such cases.
>
> This applies to the 5.3 branch and will be reverted on TOT in a bit.
>
> BUG=632965
>
> Committed: https://crrev.com/8592c450a68581d7257c1b2002983c0092cd749a
> Cr-Commit-Position: refs/heads/master@{#38276}

TBR=ahaas@chromium.org,yangguo@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=632965

Review-Url: https://codereview.chromium.org/2225773002
Cr-Commit-Position: refs/heads/master@{#38414}