python-compat: adapt to Python 3.11 BC breakage with `random.sample`

As per https://docs.python.org/3/whatsnew/3.11.html#porting-to-python-3-11:

"The population parameter of `random.sample()` must be a sequence, and
automatic conversion of sets to lists is no longer supported.
Also, if the sample size is larger than the population size,
a `ValueError` is raised"

mercurial/setdiscovery.py

@@ -99,9 +99,9 b' def _limitsample(sample, desiredlen, ran'
     """
     if len(sample) <= desiredlen:
         return sample
+    sample = list(sample)
     if randomize:
         return set(random.sample(sample, desiredlen))
-    sample = list(sample)
     sample.sort()
     return set(sample[:desiredlen])