Add missing value to the AuthpolicyErrorType UMA enum

The AuthpolicyErrorType UMA enum was missing the value
ERROR_OU_CONSTRAINT_VIOLATION, in order to match the ErrorType message
defined in active_directory_info.proto.

Bug: 1063026
Change-Id: Id0b36a8a43d5e02bf9d3d360e93c11f713820b0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2109702Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Felipe Andrade <fsandrade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#751964}

tools/metrics/histograms/enums.xml

@@ -3880,6 +3880,9 @@ Unknown properties are collapsed to zero. -->
       label="Domain join failed because KDC does not support encryption
              types."/>
   <int value="37" label="kpasswd exited with unspecified error."/>
+  <int value="38"
+      label="Setting computer organizational unit failed with constraint
+             violation"/>
 </enum>
 
 <enum name="AutocheckoutBubble">