update go-libp2p-pubsub to v0.5.6

[vyzo]

release notes:

• https://github.com/libp2p/go-libp2p-pubsub/releases/tag/v0.5.6
• https://github.com/libp2p/go-libp2p-pubsub/releases/tag/v0.5.5

[codecov]

Codecov Report

Merging #7581 (758b54f) into master (d9fd1d9) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7581      +/-   ##
==========================================
- Coverage   39.89%   39.84%   -0.05%     
==========================================
  Files         633      633              
  Lines       67098    67098              
==========================================
- Hits        26771    26738      -33     
- Misses      35731    35756      +25     
- Partials     4596     4604       +8     

Impacted Files	Coverage Δ
chain/events/message_cache.go	87.50% <0.00%> (-12.50%)	⬇️
storage/wdpost_sched.go	75.24% <0.00%> (-11.89%)	⬇️
extern/sector-storage/manager_calltracker.go	57.70% <0.00%> (-4.85%)	⬇️
chain/sub/incoming.go	54.43% <0.00%> (-3.38%)	⬇️
chain/events/events_called.go	83.90% <0.00%> (-1.96%)	⬇️
chain/stmgr/searchwait.go	66.02% <0.00%> (-1.29%)	⬇️
chain/gen/gen.go	68.61% <0.00%> (-1.24%)	⬇️
storage/wdpost_changehandler.go	97.64% <0.00%> (-0.95%)	⬇️
extern/sector-storage/sched.go	83.95% <0.00%> (-0.83%)	⬇️
storage/wdpost_run.go	69.62% <0.00%> (-0.64%)	⬇️
... and 12 more

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