Remove spec

[lightclient]

I opened a PR to the execution-apis repository to track the Builder API specification, so we should probably remove it from this repository.

ethereum/execution-apis#209

[codecov-commenter]

Codecov Report

Merging #98 (0a2a17c) into main (aeb7489) will increase coverage by 0.18%.
The diff coverage is 58.04%.

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
+ Coverage   59.85%   60.03%   +0.18%     
==========================================
  Files           8        7       -1     
  Lines         700      518     -182     
==========================================
- Hits          419      311     -108     
+ Misses        219      155      -64     
+ Partials       62       52      -10     

Flag	Coverage Δ
unittests	60.03% <58.04%> (+0.18%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
lib/rpcserver.go	25.53% <25.53%> (ø)
lib/gen_executionpayloadheader.go	59.45% <44.82%> (ø)
lib/gen_executionpayload.go	59.45% <59.45%> (ø)
lib/gen_getheaderresponse.go	64.70% <64.70%> (ø)
lib/gen_getheaderresponsemsg.go	66.66% <66.66%> (ø)
lib/service.go	66.48% <71.00%> (+17.50%)	⬆️
lib/jsonrpc.go	100.00% <0.00%> (+33.33%)	⬆️

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[metachris]

will merge once ethereum/execution-apis#209 is merged 👍

[metachris]

Done in #121