Dont declare _is_utc in tslib

Author: jbrockmendel

pandas/_libs/tslib.pxd

@@ -3,7 +3,6 @@ from numpy cimport ndarray, int64_t
 cdef convert_to_tsobject(object, object, object, bint, bint)
 cpdef convert_to_timedelta64(object, object)
 cpdef object maybe_get_tz(object)
-cdef bint _is_utc(object)
 cdef bint _is_tzlocal(object)
 cdef object _get_dst_info(object)
 cdef bint _nat_scalar_rules[6]