Fix network protocol metrics typo

[Menduist]

That's what you gain by not using typed things

[codecov]

Codecov Report

Merging #874 (086a4c3) into unstable (8d5ea43) will decrease coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #874      +/-   ##
============================================
- Coverage     83.83%   83.80%   -0.04%     
============================================
  Files            86       86              
  Lines         14969    14970       +1     
============================================
- Hits          12550    12546       -4     
- Misses         2419     2424       +5     

Impacted Files	Coverage Δ
libp2p/muxers/mplex/lpchannel.nim	83.13% <ø> (+0.09%)	⬆️
libp2p/protocols/secure/secure.nim	71.15% <0.00%> (-3.85%)	⬇️
libp2p/muxers/mplex/mplex.nim	87.70% <0.00%> (-0.82%)	⬇️
libp2p/transports/wstransport.nim	85.71% <0.00%> (ø)