Simplify DatabaseRegion.iisModified(by:)
Simplify DatabaseRegion.iisModified(by:)

There is no "fast path" any longer. Performance impact should be minimal since most observers call `stopObservingDatabaseChangesUntilNextTransaction` on first impactful change anyway.

groue/GRDB.swift,groue/GRDB.swift,groue/GRDB.swift,groue/GRDB.swift