Renable svg/custom/relative-sized-image.xhtml flakiness expectation
Renable svg/custom/relative-sized-image.xhtml flakiness expectation

The expectation was temporarily disabled when a NeedsRebaseline
conflicted withe the expectations.

Renable it because the conflicting NeedsRebaseline has been resolved.

BUG=439840
TBR=wangxianzhu@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/800343003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@187109 bbb929c8-8fbe-4397-9dbb-9b2b20218538

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk