go/oasis-node/cmd: Remove retry functionality from staking CLI commands

[tjanez]

As mentioned #3111 (comment), the retry functionality is not needed since the staking client waits for a response from the gRPC server.

[codecov]

Codecov Report

Merging #3113 into master will increase coverage by 0.16%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##           master    #3113      +/-   ##
==========================================
+ Coverage   68.36%   68.52%   +0.16%     
==========================================
  Files         372      372              
  Lines       36910    36882      -28     
==========================================
+ Hits        25234    25275      +41     
+ Misses       8436     8352      -84     
- Partials     3240     3255      +15     

Impacted Files	Coverage Δ
go/oasis-node/cmd/common/flags/flags.go	94.11% <ø> (-0.62%)	⬇️
go/oasis-node/cmd/stake/account.go	56.98% <ø> (-0.24%)	⬇️
go/oasis-node/cmd/stake/stake.go	51.66% <25.00%> (-17.57%)	⬇️
go/runtime/host/protocol/connection.go	61.38% <0.00%> (-4.64%)	⬇️
go/runtime/tagindexer/tagindexer.go	68.47% <0.00%> (-4.35%)	⬇️
go/worker/keymanager/handler.go	60.37% <0.00%> (-3.78%)	⬇️
go/storage/metrics.go	71.73% <0.00%> (-3.27%)	⬇️
go/roothash/api/commitment/pool.go	70.54% <0.00%> (-3.25%)	⬇️
go/storage/mkvs/iterator.go	81.87% <0.00%> (-2.50%)	⬇️
go/runtime/transaction/transaction.go	74.54% <0.00%> (-2.43%)	⬇️
... and 22 more

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