Remove 'conflicts:' from the search autocomplete

The second most frequent error for JS errors is "Server error:
'conflicts:' operator is not supported by the server.

Change-Id: I5f8838011656d3c08606687a39f90f384ed49361
diff --git a/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.ts b/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.ts
index 78c1ebd..aaeb924 100644
--- a/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.ts
+++ b/polygerrit-ui/app/elements/core/gr-search-bar/gr-search-bar.ts
@@ -55,7 +55,6 @@
   'commentby:',
   'commit:',
   'committer:',
-  'conflicts:',
   'deleted:',
   'delta:',
   'dir:',