updater: use IID_PPV_ARGS macro when creating INetworkCostManager.

Also, remove TODO comment.

Bug: 1254492
Change-Id: I4fac61c46fd4bcb121c087821d76981bd49468ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4550437


Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Auto-Submit: Sorin Jianu <sorin@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1147158}