BURs: fix tags field not finding all BURs with that tag.

Fix the Tags field in the BUR search form not finding all BURs
mentioning that tag. Specifically, tags that were part of a mass update,
and that were prefixed with `~` or `-` (OR tags and NOT tags), weren't
indexed as tags affected by the BUR.

This requires re-running script/fixes/064_initialize_bulk_update_request_tags.rb
to fix old BURs.

test/unit/bulk_update_request_test.rb

@@ -546,7 +546,7 @@ class BulkUpdateRequestTest < ActiveSupport::TestCase
         assert_equal(%w[aaa bbb], @bur.tags)
 
         @bur.update!(script: @script)
-        assert_equal(%w(000 111 222 333 444 aaa bbb ccc ddd eee iii), @bur.tags)
+        assert_equal(%w(000 111 222 333 444 555 aaa bbb ccc ddd eee fff ggg iii), @bur.tags)
       end
     end