SQLite: Make patch-add-3d.sql a no-op

On a fresh install, update.php will apply patch-add-3d.sql even though
it doesn't need to. But this partially wipes out the new schema from
tables.sql, and the omnibus comment and actor table patched don't detect
this, leading to image, oldimage, and filearchive missing the new
fields.

Since SQLite doesn't actually care about the values in the ENUM type
(it's just an alias for TEXT), let's just make patch-add-3d.sql do
nothing.

Change-Id: I335cb8d9626f535a66b0fe18e051640b22848ef7