Minor change to rename helper function in Extract ops

[algochoi]

Summary

Changes a helper function name from opExtractNBits to opExtractNBytes to reflect actual behavior.

[codecov-commenter]

Codecov Report

Merging #2554 (4f8be14) into master (01248d2) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2554      +/-   ##
==========================================
+ Coverage   46.89%   46.94%   +0.04%     
==========================================
  Files         346      348       +2     
  Lines       55616    55634      +18     
==========================================
+ Hits        26081    26117      +36     
+ Misses      26580    26569      -11     
+ Partials     2955     2948       -7     

Impacted Files	Coverage Δ
data/transactions/logic/eval.go	90.72% <100.00%> (ø)
cmd/algoh/blockWatcher.go	77.77% <0.00%> (ø)
libgoal/lockedFileUnix.go	0.00% <0.00%> (ø)
util/db/fullfsync_darwin.go	100.00% <0.00%> (ø)
network/wsNetwork.go	60.92% <0.00%> (+0.18%)	⬆️
util/db/dbutil.go	39.54% <0.00%> (+0.56%)	⬆️
catchup/service.go	70.34% <0.00%> (+0.78%)	⬆️
catchup/peerSelector.go	100.00% <0.00%> (+1.04%)	⬆️
ledger/blockqueue.go	82.18% <0.00%> (+1.14%)	⬆️
network/wsPeer.go	74.37% <0.00%> (+2.22%)	⬆️
... and 5 more

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