fix: remove strange Ping

[ulbqb]

Description

Ping function is used in only test. But it always returns nil which is meaningless. So I removed it. Removing has no problem for spec.

https://github.com/informalsystems/tendermint-rs/blob/main/docs/architecture/adr-011-validator-crate.md

Ping History:

• https://github.com/tendermint/tendermint/pull/2568/files#diff-21b28fcbc3e3f755a54323769b10510e7c144d521e05d065dac8f8360928baa7R79
• https://github.com/tendermint/tendermint/pull/3351/files#diff-4c9597947b77f66a0436065caefa4420fc94bf63faefe22979db4bbfd9720aaeL131
• https://github.com/tendermint/tendermint/pull/3370/files#diff-f26cb79f69b0f0824a4e09e13ce477efdfc05d9ae1101d6cee5eae8ed09539edR51

It seemed to be left behind after repeated refactorings.

[codecov]

Codecov Report

Merging #523 (9753d1f) into main (280514c) will increase coverage by 0.02%.
The diff coverage is 71.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #523      +/-   ##
==========================================
+ Coverage   65.81%   65.83%   +0.02%     
==========================================
  Files         279      279              
  Lines       38057    38044      -13     
==========================================
  Hits        25048    25048              
+ Misses      11212    11201      -11     
+ Partials     1797     1795       -2     

Impacted Files	Coverage Δ
libs/os/os.go	28.78% <0.00%> (ø)
privval/retry_signer_client.go	0.00% <ø> (ø)
privval/signer_client.go	49.35% <ø> (+1.62%)	⬆️
rpc/jsonrpc/client/http_json_client.go	20.47% <0.00%> (ø)
rpc/jsonrpc/client/http_uri_client.go	0.00% <0.00%> (ø)
abci/example/kvstore/helpers.go	100.00% <100.00%> (ø)
config/toml.go	74.19% <100.00%> (ø)
consensus/state.go	73.47% <100.00%> (-0.18%)	⬇️
crypto/armor/armor.go	47.82% <100.00%> (ø)
libs/cli/helper.go	61.44% <100.00%> (ø)
... and 23 more

[torao]

LGTM

[tnasu]

I don't know why, but I've confirmed to stop using Ping() in history. So I agree to remove Ping.

• Make Ping() and use it for monitoring the connection alive
  • privval: Add IPCPV and fix SocketPV tendermint/tendermint#2568
    • https://github.com/tendermint/tendermint/pull/2568/files#diff-21b28fcbc3e3f755a54323769b10510e7c144d521e05d065dac8f8360928baa7R79
• Refator IPCVal to SocketVal
  • Close and retry a RemoteSigner on err tendermint/tendermint#2923
    • https://github.com/tendermint/tendermint/pull/2923/files#diff-96c36ede118b77af92b95fa88f48345ba89132e516d588b9cc07d35283418394R150
• Refactor to divide SocketVal into SignerRemote and SignerValidatorEndpoint
  • Improve Remote Signer implementation tendermint/tendermint#3351
    • https://github.com/tendermint/tendermint/pull/3351/files#diff-2a787d21700c92e9c1b812d4c4c439e471c28ee4369640f9fd399b621d2ba035R142
• Refactor SignerValidatorEndpoint to SignerListenerEndpoint and stop using Ping()
  • Refactoring Remote signers tendermint/tendermint#3370
    • https://github.com/tendermint/tendermint/pull/3370/files#diff-b15f92c590eafe71fca1b0b951414e66e25cc8dc307522bf8cbdf99ab198ec1cR188

In addition, the current Ping() is a strange implementation since the first version.
https://github.com/tendermint/tendermint/pull/3370/files#diff-f26cb79f69b0f0824a4e09e13ce477efdfc05d9ae1101d6cee5eae8ed09539edR54-R63