Update spec tests and fix parsing of "userListen" entries

Author: dconeybe

Firestore/Example/Tests/SpecTests/FSTSpecTests.mm

@@ -327,11 +327,11 @@ - (DocumentViewChange)parseChange:(NSDictionary *)jsonDoc ofType:(DocumentViewCh
 
 #pragma mark - Methods for doing the steps of the spec test.
 
-- (void)doListen:(NSArray *)listenSpec {
-  Query query = [self parseQuery:listenSpec[1]];
+- (void)doListen:(NSDictionary *)listenSpec {
+  Query query = [self parseQuery:listenSpec[@"query"]];
   TargetId actualID = [self.driver addUserListenerWithQuery:std::move(query)];
 
-  TargetId expectedID = [listenSpec[0] intValue];
+  TargetId expectedID = [listenSpec[@"targetId"] intValue];
   XCTAssertEqual(actualID, expectedID, @"targetID assigned to listen");
 }