[0.29] deprecation warning for "from x cimport class A" syntax (#4905)
[0.29] deprecation warning for "from x cimport class A" syntax (#4905)

Unused/rarely used syntax which we plan to remove in Cython 3.
See https://github.com/cython/cython/pull/4904
cython/cython,cython/cython,cython/cython,cython/cython