Tests: remove testswarm grunt task

Closes gh-2263

Author: timmywil

build/tasks/testswarm.js

@@ -396,8 +396,6 @@ QUnit.test( "collision: fit, no collision", function( assert ) {
 }, "with offset" );
 } );
 
-// Currently failing in IE8 due to the iframe used by TestSwarm
-if ( !/msie [\w.]+/.exec( navigator.userAgent.toLowerCase() ) ) {
 QUnit.test( "collision: fit, collision", function( assert ) {
 assert.expect( 2 + ( scrollTopSupport() ? 1 : 0 ) );
 
@@ -428,7 +426,6 @@ QUnit.test( "collision: fit, collision", function( assert ) {
 win.scrollTop( 0 ).scrollLeft( 0 );
 }
 } );
-}
 
 QUnit.test( "collision: flip, no collision", function( assert ) {
 assert.expect( 2 );