Add LINT to SearchPolicyConflictType

This CL adds a simple LINT statement for SearchPolicyConflictType to
ensure changes remain consistent among the histogram and enum
definition.

NO_IFTTT=false positive on introduction of LINT.IfChange

Bug: 409590861
Change-Id: Ifa2fb3a61dc70c8c092b3775ce319a90a1b33d14
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6443858
Reviewed-by: Tomasz Wiszkowski <ender@google.com>
Commit-Queue: Ananya Seelam <ananyaseelam@google.com>
Reviewed-by: manuk hovanesian <manukh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1446059}