Add 'Accepted with Guest' to SigninInterceptResult in enums.xml.

Fixes a forgotten value in enums.xml.

Bug: 1157764
Change-Id: I4e8f60588f095f31349ad032d89c2cea83fecac8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626653
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Commit-Queue: David Roger <droger@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842972}

tools/metrics/histograms/enums.xml

@@ -68740,6 +68740,7 @@ https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_2.7.1.pdf
   <int value="1" label="Declined"/>
   <int value="2" label="Ignored"/>
   <int value="3" label="Not displayed"/>
+  <int value="4" label="Accepted with Guest"/>
 </enum>
 
 <enum name="SigninInterceptSessionStartupResult">