Problem: unnecessary use of REST API instead of grpc-web (get_account_balance part)

[stevenatcrypto]

Part of issue #511 (will fix get_account_details in another PR)

Replace REST API with grpc-web for get_account_balance functions.

PR Checklist:

• Have you read the CONTRIBUTING.md?
• Does your PR follow the C4 patch requirements?
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• If your changes affect public APIs, does your PR follow the C4 evolution of public contracts?
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• If you are contributing for the first time, please read the agreement in CONTRIBUTING.md now and add a comment to this pull request stating that your PR is in accordance with the Developer's Certificate of Origin.

[codecov-commenter]

Codecov Report

Base: 43.83% // Head: 43.97% // Increases project coverage by +0.14% 🎉

Coverage data is based on head (2b7928d) compared to base (9bd0ca6).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #663      +/-   ##
==========================================
+ Coverage   43.83%   43.97%   +0.14%     
==========================================
  Files          45       46       +1     
  Lines        8968     8939      -29     
==========================================
  Hits         3931     3931              
+ Misses       5037     5008      -29     

Impacted Files	Coverage Δ
bindings/cpp/src/lib.rs	0.14% <0.00%> (+<0.01%)	⬆️
common/src/node/cosmos_sdk.rs	0.00% <0.00%> (ø)
common/src/node/cosmos_sdk/balance_query.rs	0.00% <0.00%> (ø)

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[tomtau]

looks ok, but some binding examples (android, JS/Wasm...) may still have old URLs?