[metrics] Add enum values for Android kernels.

4.19 and 5.4 are Android kernel versions, visible in reported metrics,
but not in enums.xml.

Change-Id: Ib09ded38501345c2df17743c4da5c4eb741f0aa6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2424244Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809356}

tools/metrics/histograms/enums.xml

@@ -1819,6 +1819,8 @@ Unknown properties are collapsed to zero. -->
   <int value="262154" label="4.10"/>
   <int value="262157" label="4.13"/>
   <int value="262158" label="4.14"/>
+  <int value="262163" label="4.19"/>
+  <int value="327684" label="5.4"/>
 </enum>
 
 <enum name="AndroidManageSpaceButton">