CLN: don't hard code min_count in call to _libs.groupby.group_nth

Author: arw2019

pandas/core/groupby/ops.py

@@ -603,8 +603,7 @@ def _aggregate(
     ):
         if agg_func is libgroupby.group_nth:
             # different signature from the others
-            # TODO: should we be using min_count instead of hard-coding it?
-            agg_func(result, counts, values, comp_ids, rank=1, min_count=-1)
+            agg_func(result, counts, values, comp_ids, rank=1, min_count=min_count)
         else:
             agg_func(result, counts, values, comp_ids, min_count)