Trac #33234: fix python-3.10 deprecation warning in polynomial roots.

We're passing a float to python's random.randrange, and randrange
isn't happy about that in python-3.10:

  DeprecationWarning: non-integer arguments to randrange() have been
  deprecated since Python 3.10 and will be removed in a subsequent
  version

Fortunately the float in question is integral, and we can simply
replace

  qdiv = div / 4

with

  qdiv = div // 4

to get an int that randrange will tolerate.

Author: orlitzky

src/sage/rings/polynomial/real_roots.pyx

@@ -408,9 +408,9 @@ cdef class interval_bernstein_polynomial:
         # A different algorithm here might be more efficient.
 
         div = 1024
-        while self.degree() >= div//4:
+        while self.degree() >= (div // 4):
             div = div * 2
-        qdiv = div/4
+        qdiv = div // 4  # divides evenly since div = 1024*2^k
         rand = Integer(ctx.random.randrange(qdiv, 3*qdiv)) / div
         (p1, p2, ok) = self.de_casteljau(ctx, rand)
         ctx.dc_log_append(("div" + self._type_code(), self.scale_log2, self.bitsize, rand, ok, logging_note))