[libunwind] Ensure zaDisable() is called in jumpto/returnto (NFC) (#167674)

This is an NFC for now, as the SME checks for macOS platforms are not
implemented, so zaDisable() is a no-op, but both paths for resuming from
an exception should disable ZA.

This is a fixup for a recent change in #165066.

GitOrigin-RevId: d2a2b169f6cdfc2864f83ebc221dc771a9a1697d