Rate limit fixes

[diegomrsantos]

• "e2e - GossipSub should not rate limit decodable messages below the size allowed" test was flaky because sometimes the test would behave differently from what was expected due to failed signature verification. Always disabling the signature hopefully will fix it.
• Another test was added for the case when the rate limit happens due to invalid domain messages.

[codecov]

Codecov Report

Merging #965 (3a46834) into unstable (60f9536) will increase coverage by 0.07%.
Report is 1 commits behind head on unstable.
The diff coverage is 71.42%.

@@             Coverage Diff              @@
##           unstable     #965      +/-   ##
============================================
+ Coverage     83.20%   83.28%   +0.07%     
============================================
  Files            91       91              
  Lines         15308    15312       +4     
============================================
+ Hits          12737    12752      +15     
+ Misses         2571     2560      -11     

Files	Coverage Δ
libp2p/protocols/pubsub/gossipsub/scoring.nim	91.66% <100.00%> (+1.53%)	⬆️
libp2p/protocols/pubsub/gossipsub.nim	88.08% <33.33%> (+0.20%)	⬆️

... and 7 files with indirect coverage changes