txHandler: disable canonical hashmap by default

[algorandskiy]

Summary

Disabled the second level check after performance concerns and TX vs agreement messages processing competition.

Test Plan

Existing tests

[codecov]

Codecov Report

Merging #4877 (674509c) into master (c0c5a94) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4877      +/-   ##
==========================================
- Coverage   54.01%   54.00%   -0.02%     
==========================================
  Files         426      426              
  Lines       53425    53425              
==========================================
- Hits        28859    28852       -7     
- Misses      22305    22311       +6     
- Partials     2261     2262       +1     

Impacted Files	Coverage Δ
config/localTemplate.go	43.75% <ø> (ø)
ledger/blockqueue.go	85.63% <0.00%> (-2.88%)	⬇️
network/wsPeer.go	67.06% <0.00%> (-2.39%)	⬇️
network/wsNetwork.go	64.74% <0.00%> (-0.18%)	⬇️
ledger/acctupdates.go	69.48% <0.00%> (+0.24%)	⬆️
ledger/testing/randomAccounts.go	57.23% <0.00%> (+0.61%)	⬆️
cmd/tealdbg/debugger.go	73.49% <0.00%> (+0.80%)	⬆️
ledger/tracker.go	75.10% <0.00%> (+0.84%)	⬆️
catchup/peerSelector.go	100.00% <0.00%> (+1.04%)	⬆️

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