Fix serialization of parameters in RpcClient::get_block_production_with_config (backport #18998)

[mergify]

This is an automatic backport of pull request #18998 done by Mergify.
Cherry-pick of 58f3952 has failed:

On branch mergify/bp/v1.7/pr-18998
Your branch is up to date with 'origin/v1.7'.

You are currently cherry-picking commit 58f395257.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   client/src/rpc_client.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   client/src/mock_sender.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[solana-grimes]

😱 New commits were pushed while the automerge label was present.

[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[mergify]

automerge label removed due to a CI failure

[codecov]

Codecov Report

Merging #19000 (6a0363e) into v1.7 (8934a39) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##             v1.7   #19000   +/-   ##
=======================================
  Coverage    82.3%    82.3%           
=======================================
  Files         436      436           
  Lines      123156   123178   +22     
=======================================
+ Hits       101360   101390   +30     
+ Misses      21796    21788    -8     

[t-nelson]

🎉

[CriesofCarrots]

Phew, finally! Thanks for giving the one a kick, @t-nelson