Core: Adjust comments & tests after dropping Safari 6 support

Support comments that mentioned only Safari < 7 were checked & updated
to account for bugs existing in newer versions as well; Safari 6 support
test results were removed.

Refs gh-2482

test/unit/css.js

@@ -1121,7 +1121,7 @@ test( "show() after hide() should always set display to initial value (#14750)",
 	equal( div.css( "display" ), "list-item", "should get last set display value" );
 });
 
-// Support: IE < 11, Safari < 7
+// Support: IE < 11
 // We have to jump through the hoops here in order to test work with "order" CSS property,
 // that some browsers do not support. This test is not, strictly speaking, correct,
 // but it's the best that we can do.

test/unit/support.js

@@ -143,7 +143,7 @@ testIframeWithCallback( "Check CSP (https://developer.mozilla.org/en-US/docs/Sec
 			"radioValue": true,
 			"reliableMarginRight": true
 		};
-	} else if ( /(6|7)\.0(\.\d+|) safari/i.test( userAgent ) ) {
+	} else if ( /7\.0(\.\d+|) safari/i.test( userAgent ) ) {
 		expected = {
 			"ajax": true,
 			"boxSizingReliable": true,