go/oasis-node/cmd: Fix output of stake account validate_address cmd

[tjanez]

Add missing newline to the verbose output when the account address is valid.

[codecov]

Codecov Report

Merging #3589 (f9a21e0) into master (7e19cd8) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3589      +/-   ##
==========================================
+ Coverage   66.58%   66.60%   +0.02%     
==========================================
  Files         377      377              
  Lines       34562    34562              
==========================================
+ Hits        23013    23021       +8     
+ Misses       8230     8226       -4     
+ Partials     3319     3315       -4     

Impacted Files	Coverage Δ
go/oasis-node/cmd/stake/account.go	54.71% <100.00%> (ø)
go/consensus/tendermint/api/api.go	74.66% <0.00%> (-10.67%)	⬇️
go/consensus/tendermint/api/errors.go	90.00% <0.00%> (-10.00%)	⬇️
go/worker/common/committee/node.go	72.34% <0.00%> (-6.39%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	75.00% <0.00%> (-5.00%)	⬇️
go/consensus/tendermint/roothash/roothash.go	68.49% <0.00%> (-4.39%)	⬇️
go/consensus/tendermint/full/light.go	48.93% <0.00%> (-4.26%)	⬇️
go/consensus/tendermint/apps/staking/state/gas.go	81.13% <0.00%> (-3.78%)	⬇️
go/storage/mkvs/lookup.go	72.04% <0.00%> (-2.16%)	⬇️
go/worker/storage/committee/checkpoint_sync.go	72.76% <0.00%> (-1.95%)	⬇️
... and 32 more

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