Remove incorrect getComputedStyle() test for ::first-line

Only a few properties apply to ::first-line, but that does not mean the
computed value is affected. The test incorrectly assumed the computed
value of vertical-align for ::first-line is reset to its initial value.

Notified the author here:

WebKit/WebKit#48454 (comment)

Bug: 503879985
Change-Id: I1f37b490a0d4eef452c89242d0e962a7b834e6a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7900679
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Steinar H Gunderson <sesse@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1642181}

Author: lilles