[GTK] Remove some obsolete expected failures.

[GTK] Remove some obsolete expected failures.
https://bugs.webkit.org/show_bug.cgi?id=175674

Unreviewed test gardening.

Patch by Ms2ger <Ms2ger@gmail.com> on 2017-08-18

* platform/gtk/TestExpectations:
  - imported/w3c/web-platform-tests/IndexedDB/keyorder.htm: passing since r204279.
  - imported/w3c/web-platform-tests/resource-timing/rt-cors.html: passing since r212944 and r212993.
  - imported/w3c/web-platform-tests/resource-timing/rt-cors.worker.html: passing since r212944 and r212993.
  - imported/w3c/web-platform-tests/webrtc/getstats.html: passing since test update and rebaseline in r217225.
  - mathml/opentype/large-operators-displaystyle-dynamic.html: used to be flaky, seems to be passing consistently now.
  - media/media-fullscreen-return-to-inline.html: likely passing since r218270.
  - media/video-fast-seek.html: passing since r207879-r207894.
  - platform/gtk/scrollbars/main-frame-scrollbar-horizontal-wheel-scroll.html: passing since r205075.
  - security/contentSecurityPolicy/video-with-data-url-allowed-by-media-src-star.html: flaky.
  - storage/indexeddb/cursor-key-order.html: likely passing since r209135.
  - svg/dom/SVGScriptElement/script-change-externalResourcesRequired-while-loading.svg: flaky.
  - svg/repaint/add-outline-property-on-root.html: passing since r211277
  - svg/repaint/remove-outline-property-on-root.html: passing since r211277

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220911 268f45cc-cd09-0410-ab3c-d52691b4dbfc