[css-nav-1] Update the status of issues

- Remove the resolved issue (#28 in WICG)
- Fix the link of the issue from WICG repo to CSSWG repo

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1006,7 +1006,7 @@ and aims for as much detail as necessary
 to fully define the behavior.
 </div>
 
-Issue(19): The following currently does not account
+Issue(w3c/csswg-drafts#3376): The following currently does not account
 for <a href="https://github.com/WICG/overscroll-behavior">the proposed overscroll-behavior specification</a>.
 
 
@@ -1114,8 +1114,6 @@ To run the <dfn>spatial navigation steps</dfn> in <var>direction</var>, do the f
                 2. Set <var>eventTarget</var> be <var>searchOrigin</var>
                 3. Set <var>container</var> to the nearest ancestor of <var>searchOrigin</var> that is a <a>spatial navigation container</a>.
                 4. Return to the step labeled <i>loop</i>.
-
-                Issue(28): is it sane from a security standpoint that this propagates up from iframes?
             * Else, set <var>container</var> to its closest ancestor that is itself a <a>spatial navigation container</a>
                 and return to the step labeled <i>loop</i>.
 9. Let <var>bestCandidate</var> be the result of <a>selecting the best candidate</a>