Add enum value for error update download canceled per policy

This CL adds error code for update download canceled due to
DeviceAutoUpdateTimeRestrictions policy to the
enum so that it can be reflected in the histogram. This error code is
already added in update engine code in the following CL -
https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2567121

Bug: chromium:1117450
Change-Id: I69d109553c28a4948d725183293640d8eb044731
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2584984Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Saurabh Nijhara <snijhara@google.com>
Cr-Commit-Position: refs/heads/master@{#836042}

tools/metrics/histograms/enums.xml

@@ -74457,6 +74457,7 @@ Full version information for the fingerprint enum values:
   <int value="61" label="kErrorNotEnoughSpace"/>
   <int value="62" label="kErrorDeviceCorrupted"/>
   <int value="63" label="kErrorPackageExcludedFromUpdate"/>
+  <int value="64" label="kErrorDownloadCancelledPerPolicy"/>
 </enum>
 
 <enum name="UpdateEngineInstallDateProvisioningSource">