[memory-diff] Increase threshold for call memory increased/decreased (#38674)

Noise is currently higher than our detection threshold.

Closes #38674

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/38674 from ctiller:limits 9d3f4901e4
PiperOrigin-RevId: 722842062

tools/profiling/memory/memory_diff.py

@@ -169,7 +169,7 @@ else:
     call_increase = 0
     channel_decrease = 0
     channel_increase = 0
-    call_significant = 100
+    call_significant = 200
     channel_significant = 1000
     for scenario in _SCENARIOS.keys():
         for key, value in sorted(_INTERESTING.items()):