test: TestSlowPeerDisconnect less flakey

[brianolson]

Summary

sleeping 1ms can still starve other processes sometimes.
sleep 10ms to let the test run.
test used to fail about 1/200; haven't seen a failure in several thousand now.

Test Plan

This is a test. It should be less flakey now.

[algorandskiy]

Thank you Brian

[codecov]

Codecov Report

Merging #4453 (2d7580c) into master (924d2fb) will increase coverage by 3.68%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4453      +/-   ##
==========================================
+ Coverage   51.51%   55.19%   +3.68%     
==========================================
  Files         398      398              
  Lines       50165    50165              
==========================================
+ Hits        25841    27691    +1850     
+ Misses      21934    20160    -1774     
+ Partials     2390     2314      -76     

Impacted Files	Coverage Δ
cmd/algoh/blockWatcher.go	77.77% <0.00%> (-3.18%)	⬇️
network/requestTracker.go	70.25% <0.00%> (-0.44%)	⬇️
network/wsNetwork.go	64.63% <0.00%> (+0.09%)	⬆️
ledger/internal/prefetcher/prefetcher.go	68.18% <0.00%> (+0.45%)	⬆️
node/node.go	4.43% <0.00%> (+0.47%)	⬆️
util/db/dbutil.go	44.24% <0.00%> (+0.60%)	⬆️
daemon/algod/api/server/v2/dryrun.go	70.82% <0.00%> (+0.60%)	⬆️
agreement/pseudonode.go	70.07% <0.00%> (+0.72%)	⬆️
ledger/catchpointwriter.go	57.65% <0.00%> (+0.90%)	⬆️
ledger/acctonline.go	78.36% <0.00%> (+1.05%)	⬆️
... and 112 more

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