spyder-kernels declares an build-dep on python3-ipykernel (>= 6.29.3, <<7),
which is no longer satisfyable in unstable (since ipykernel 7.1.0 was uploaded)

This was unfortunately not caught while ipykernel was in experimental,
since the autopkgtests for spyder-kernels have been failing for some
time and thus did not regress.

A test build without the upper bound did not add any new test failures,
but I did not verify any further functionality.