Removing ewk_context_default_get call

Removing ewk_context_default_get call

[Issue#] N/A
[Problem] Call to internal EWK API
[Cause] Code restored during branch merge
[Solution] Remove the call, it is not needed
[Verify] Build and run the browser, load a few tabs, close tabs

The call to ewk_context_default get was restored by mistake when performing a
merge between branches. The version in tizen branch had the code replaced with
another method to implicitly initialize EWK internal contexts.

Change-Id: If21dcc4ca40242786c22e80b7a5591a70c56ecfb