ObsoleteFiles.inc: Remove test debug file from wrong dir

Reported by: des
Reviewed by: des, emaste
Approved by: emaste (mentor)
Fixes: 88d448ec815c ("mk: Move vm stack test debug symbols")
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D48991

(cherry picked from commit e159dcc37e6f538d3d61ea3b2d08b052cf0e0ced)