Most DBs apart from SQLite will use a default Collation that is not case insensitive.
This means that SearchIssuesByKeyword becomes case sensitive for db indexing - in
contrast to the bleve and elastic indexers.
This PR simply uses UPPER(...) to do the LIKE - and although it may be more efficient
to change collations this would be a non-trivial task.
Fix#13663
Signed-off-by: Andrew Thornton <art27@cantab.net>