Remove forward reference overload in KV RPC

[canepat]

This PR removes the BidirectionalStreamingRpc::send_response method overload using forward reference because this is the one change causing repeated failures on TSAN CI job, namely here and here.

[codecov]

Codecov Report

Merging #640 (ae91ef1) into master (f4f6759) will increase coverage by 0.04%.
The diff coverage is 88.23%.

@@            Coverage Diff             @@
##           master     #640      +/-   ##
==========================================
+ Coverage   82.36%   82.40%   +0.04%     
==========================================
  Files         173      173              
  Lines       14996    14996              
==========================================
+ Hits        12351    12357       +6     
+ Misses       2645     2639       -6     

Impacted Files	Coverage Δ
node/silkworm/rpc/call.hpp	93.23% <ø> (ø)
node/silkworm/rpc/kv_calls.cpp	87.39% <88.23%> (ø)
core/silkworm/crypto/sha-256.c	51.74% <0.00%> (+0.49%)	⬆️
core/silkworm/execution/evm.cpp	96.09% <0.00%> (+0.82%)	⬆️

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[mriccobene]

Ok