Remove the ProposalPending internal slot (for now)

This slot is only needed once method(s) are added to
RTCIceTransport to perform ICE actions, eg. pruneCandidatePair().
Then the slot is used to guard against performing another
action while a proposal is pending resolution.

So defer adding the slot until methods are added.

index.html

@@ -704,14 +704,6 @@ <h3>
       The {{RTCIceTransport}} interface is defined in [[WEBRTC]]. This document extends that interface to allow an
       application to observe and affect certain actions that an <dfn>ICE agent</dfn> [[RFC5245]] performs.
     </p>
-    <p>
-      Add the following internal slots to the {{RTCIceTransport}} object:
-    </p>
-    <ul>
-      <li>
-        <dfn class=export data-dfn-for="RTCIceTransport">[[\ProposalPending]]</dfn> initialized to <code>false</code>.
-      </li>
-    </ul>
     <p>
       When the [= ICE agent =] has selected a candidate pair to prune, the [= user agent =] MUST [= queue a task =] to <dfn id="rtcicetransport-propose-prune">propose a candidate pair pruning</dfn>:
     </p>
@@ -737,11 +729,6 @@ <h3>
           Let |candidatePair:RTCIceCandidatePair| be the candidate pair which is being proposed for pruning.
         </p>
       </li>
-      <li>
-        <p>
-          Set |transport|.{{RTCIceTransport/[[ProposalPending]]}} to <code>true</code>.
-        </p>
-      </li>
       <li>
         <p>
           Let |accepted:boolean| be the result of [= fire an event | firing an event =] named
@@ -750,11 +737,6 @@ <h3>
           attribute initialized to |candidatePair|.
         </p>
       </li>
-      <li>
-        <p>
-          Set |transport|.{{RTCIceTransport/[[ProposalPending]]}} to <code>false</code>.
-        </p>
-      </li>
       <li>
         <p>
           If |accepted| is <code>false</code>, instruct the [= ICE agent =] to not prune the candidate pair indicated by |candidatePair|, and instead continue to send and respond to ICE connectivity checks on the candidate pair as before.