top_k sampler: Fix int check for older Pythons

Author: turboderp

exllamav3/generator/sampler/custom.py

@@ -219,7 +219,7 @@ class SS_TopK(SS_Base):
     Mask out all but the top K most likely tokens
     """
     def __init__(self, top_k: int):
-        assert top_k.is_integer(), "top_k value must be integer"
+        assert isinstance(top_k, int) or top_k.is_integer(), "top_k value must be integer"
         self.top_k = int(top_k)
 
     def run(self, state: SamplingState):