webrtc wpt: rename tests that check createOffer/createAnswer return value
and modernize one of them
BUG=chromium:337071657
Change-Id: Id02b570639cee026727771545899f020f3e858a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5512699
Reviewed-by: Harald Alvestrand hta@chromium.org
Reviewed-by: Guido Urdaneta guidou@chromium.org
Commit-Queue: Philipp Hancke philipp.hancke@googlemail.com
Cr-Commit-Position: refs/heads/main@{#1296825}