Update nightly main benchmark thresholds (#3187)

### Motivation:

Nightly main benchmarks have improved allocations, we should lock in the
win.

### Modifications:

Update nightly main benchmark thresholds

### Result:

Thresholds reflect gains, passing CI.

Author: rnro

Benchmarks/Thresholds/nightly-main/NIOPosixBenchmarks.TCPEchoAsyncChannel.p90.json

@@ -1,3 +1,3 @@
 {
-  "mallocCountTotal" : 164371
-}
+  "mallocCountTotal": 82000
+}