Get rid of two left-over special-cases for wasm scripts that have (or
don't have) a SourceMapURL attached to them.

Bug: chromium:1013527
Change-Id: I51bab8074011299e6f0d1fd32d93e4cb559bd476
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2013113Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Philip Pfaffe <pfaffe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65914}