fix(ts): correctly type `unstable_getServerSession` (#6560)
* fix: type of unstable_getServerSession
Signed-off-by: Vu Van Dung <me@joulev.dev>
* Apply suggestions from code review
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Signed-off-by: Vu Van Dung <me@joulev.dev>
Co-authored-by: Balázs Orbán <info@balazsorban.com>
