Revert "Add dominant/latest version index to...

Revert "Add dominant/latest version index to PaintTiming.NavigationToFirstContentfulPaint UKM event."

This reverts commit 83bbeb87.

Reason for revert: impact on pipeline

Original change's description:
> Add dominant/latest version index to PaintTiming.NavigationToFirstContentfulPaint UKM event.
> 
> Change-Id: Ib63a04cc663011872f60bd04be420b3207dffb29
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869451
> Auto-Submit: Brian White <bcwhite@chromium.org>
> Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
> Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#708206}

TBR=rkaplow@chromium.org,bcwhite@chromium.org,sdoyon@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I7ef5bc2f83fdbf3e69fd92f053b80632c12712e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1904687Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714520}

tools/metrics/ukm/ukm.xml

@@ -6041,8 +6041,6 @@ be describing additional metrics about the same event.
     <aggregation>
       <history>
         <index fields="profile.country"/>
-        <index fields="profile.is_dominant_version"/>
-        <index fields="profile.is_latest_version"/>
         <statistics>
           <quantiles type="std-percentiles"/>
         </statistics>