histograms: removes two v8 histograms

v8 patch is here:
https://chromium-review.googlesource.com/c/v8/v8/+/3399226

BUG=1257321
TEST=none

Change-Id: I8cb07edbb0c9341b385cafd9c027daecbc914077
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3399313
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#960982}

tools/metrics/histograms/metadata/v8/histograms.xml

@@ -352,6 +352,9 @@ chromium-metrics-reviews@google.com.
 
 <histogram name="V8.ContextSnapshotDecompress" units="microseconds"
     expires_after="2022-05-22">
+  <obsolete>
+    Removed 01/2022.
+  </obsolete>
   <owner>sky@chromium.org</owner>
   <owner>yukishiino@chromium.org</owner>
   <summary>
@@ -1167,6 +1170,9 @@ chromium-metrics-reviews@google.com.
 
 <histogram name="V8.SnapshotDecompress" units="microseconds"
     expires_after="2022-05-22">
+  <obsolete>
+    Removed 01/2022.
+  </obsolete>
   <owner>sky@chromium.org</owner>
   <owner>yukishiino@chromium.org</owner>
   <summary>