chore(weave): set seed in sampling test

tests/trace/test_client_trace.py

@@ -2,6 +2,7 @@
 import datetime
 import json
 import platform
+import random
 import sys
 import time
 from collections import defaultdict, namedtuple
@@ -3052,6 +3053,8 @@ def test_op_sampling_async(client):
     always_traced_calls = 0
     sometimes_traced_calls = 0
 
+    random.seed(0)
+
     @weave.op(tracing_sample_rate=0.0)
     async def never_traced(x: int) -> int:
         nonlocal never_traced_calls
@@ -3092,7 +3095,7 @@ async def sometimes_traced(x: int) -> int:
         asyncio.run(sometimes_traced(i))
     assert sometimes_traced_calls == num_runs  # Function was called every time
     num_traces = len(list(sometimes_traced.calls()))
-    assert 35 < num_traces < 65  # But only traced ~50% of the time
+    assert num_traces == 38
 
 
 def test_op_sampling_inheritance(client):