* Change the source index on posts from `(lower(source) gin_trgm_ops) WHERE source != ''`
to just `(source gin_trgm_ops)`. The WHERE clause prevented the index
from being used in source:<url> searches because we didn't specify
the `source != ''` clause in the search itself. Excluding blank
sources only saved a marginal amount of space anyway. This fixes
timeouts in source:<url> searches and in the bookmarklet (since we do
a source dupe check on the upload page too).
* Also switch from indexing `lower(name)` to `name` on pools and users.
We don't need to lowercase the column because GIN indexes can be used
with both LIKE and ILIKE queries.
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