fix(rpc): align block number input behaviour for eth_getProof (backport: #1772)

[mmsqe]

for more info: evmos#1722

Description

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For contributor use:

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• Code follows the module structure standards.
• Wrote unit and integration tests
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• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
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[codecov]

Codecov Report

Merging #233 (cb1c8a1) into release/v0.20.x-cronos (cb741e1) will decrease coverage by 0.08%.
The diff coverage is 0.00%.

@@                    Coverage Diff                     @@
##           release/v0.20.x-cronos     #233      +/-   ##
==========================================================
- Coverage                   57.20%   57.12%   -0.08%     
==========================================================
  Files                         108      108              
  Lines                       10149    10163      +14     
==========================================================
  Hits                         5806     5806              
- Misses                       4096     4110      +14     
  Partials                      247      247              

Impacted Files	Coverage Δ
rpc/backend/call_tx.go	0.00% <0.00%> (ø)
x/evm/keeper/grpc_query.go	86.98% <0.00%> (-0.60%)	⬇️