Updates Threading to 2.3.4 and SpryKit to 3.2.4.
Threading 2.3.4 fixes compilation on non-Darwin platforms and removes a Sendable constraint on a protocol requirement that Swift will reject in a future language mode. SpryKit 3.2.4 fixes argument matching for .anything and recorded closures, adds a cycle and depth guard to structural comparison, and hardens stub state under concurrent access.