kvserver: deflake TestWriteLoadStatsAccounting

This commit increases the epsilonAllowed in the test
TestWriteLoadStatsAccounting. Note that we recently increased it from
6 to 7, but this doesn't seem to have been enough.

Fixes: #158497

Release note: None

Author: iskettaneh

pkg/kv/kvserver/replica_rankings_test.go

@@ -221,7 +221,7 @@ func TestWriteLoadStatsAccounting(t *testing.T) {
 	tc := serverutils.StartCluster(t, 3, args)
 	defer tc.Stopper().Stop(ctx)
 
-	const epsilonAllowed = 6
+	const epsilonAllowed = 10
 
 	ts := tc.Server(0)
 	db := ts.DB()