Remove obsolete GS testplan - it now lives in go-graphsync

[ribasushi]

No description provided.

[ribasushi]

A conversation with @nonsense revealed this is no longer an actively-relied-upon test. The motivation of purging it from lotus is the ancient go-ipld-prime dependency it relies on.

[codecov]

Codecov Report

Merging #7469 (7784831) into master (1993efe) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7469      +/-   ##
==========================================
- Coverage   39.21%   39.15%   -0.07%     
==========================================
  Files         631      631              
  Lines       66787    66787              
==========================================
- Hits        26191    26148      -43     
- Misses      36024    36063      +39     
- Partials     4572     4576       +4     

Impacted Files	Coverage Δ
journal/types.go	86.66% <0.00%> (-13.34%)	⬇️
chain/events/observer.go	71.64% <0.00%> (-6.72%)	⬇️
chain/actors/builtin/paych/paych.go	14.77% <0.00%> (-4.55%)	⬇️
chain/exchange/peer_tracker.go	66.66% <0.00%> (-4.31%)	⬇️
node/hello/hello.go	63.63% <0.00%> (-3.41%)	⬇️
chain/store/store.go	62.66% <0.00%> (-2.84%)	⬇️
journal/fsjournal/fs.go	66.66% <0.00%> (-2.78%)	⬇️
miner/miner.go	55.29% <0.00%> (-2.32%)	⬇️
chain/sync_manager.go	66.77% <0.00%> (-0.63%)	⬇️
chain/messagepool/messagepool.go	56.93% <0.00%> (-0.62%)	⬇️
... and 9 more

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