Update UA stylesheet for view-source

r810360 crrev.com/c/2429204 changed to `white-space: pre` but
it was not effective because we have:
  white-space: pre-wrap !important;
in the UA stylesheet for view-source.

This patch updates the UA stylesheet accordingly. Verified
this change prevents line wrapping in content_shell.

Note the "!important" has been there since 2007, in the
initial commit of this file[1], but the CL message does not
explain why it is needed. This patch removes it because I do
not find it is necessary. We can bring it back if we find it
is necessary for any reasons.

[1] https://source.chromium.org/chromium/chromium/src/+/0e882e3da67c5efbd3b292a643d79867a4968950

Bug: 920571
Change-Id: Ic3221778142f697e7baa82725b3d54db397e3933
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2432706Reviewed-by: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811603}

third_party/blink/renderer/core/css/view-source.css

@@ -29,9 +29,8 @@ body {
 table {
     width: 100%;
     border-spacing: 0;
-    white-space: pre-wrap !important;
+    white-space: pre;
     margin: 0;
-    word-break: break-word;
     font-size: initial;
     font-family: monospace;
     tab-size: 4;