Unknown bits feature only needs to be validated once

[galderz]

Closes #792.

Removed the redundant validation logic.

[codecov]

Codecov Report

Merging #793 (cae0ce8) into main (e4b516d) will decrease coverage by 0.09%.
The diff coverage is 88.38%.

@@            Coverage Diff             @@
##             main     #793      +/-   ##
==========================================
- Coverage   90.80%   90.71%   -0.10%     
==========================================
  Files          38       44       +6     
  Lines       23168    24052     +884     
==========================================
+ Hits        21038    21818     +780     
- Misses       2130     2234     +104     

Impacted Files	Coverage Δ
lightning-block-sync/src/lib.rs	0.00% <0.00%> (ø)
lightning/src/ln/peer_handler.rs	49.79% <0.00%> (+0.06%)	⬆️
lightning-block-sync/src/rest.rs	65.45% <65.45%> (ø)
lightning/src/ln/msgs.rs	89.46% <75.00%> (ø)
lightning-block-sync/src/rpc.rs	78.37% <78.37%> (ø)
lightning-block-sync/src/convert.rs	92.80% <92.80%> (ø)
lightning-block-sync/src/http.rs	95.03% <95.03%> (ø)
lightning-block-sync/src/utils.rs	100.00% <100.00%> (ø)
lightning/src/routing/network_graph.rs	90.89% <100.00%> (-0.09%)	⬇️
lightning/src/ln/functional_tests.rs	96.98% <0.00%> (-0.06%)	⬇️
... and 6 more

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[ariard]

Code Review ACK 048e862

Thanks for cleaning up this!