fix: Set maximum value for SignedMsgType

[Kynea0b]

Description

TestMaxVoteBytes was tested by setting the maximum value for all of the Vote fields; only Type had no maximum value set; the maximum value for Type is ProposalType, so ProposalType is set to Type in this PR.

[codecov]

Codecov Report

Merging #531 (f6ae450) into main (2f25796) will increase coverage by 0.10%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #531      +/-   ##
==========================================
+ Coverage   66.02%   66.12%   +0.10%     
==========================================
  Files         279      279              
  Lines       38045    38045              
==========================================
+ Hits        25119    25158      +39     
+ Misses      11127    11093      -34     
+ Partials     1799     1794       -5     

Impacted Files	Coverage Δ
privval/signer_server.go	89.28% <0.00%> (-5.36%)	⬇️
privval/signer_endpoint.go	76.92% <0.00%> (-3.30%)	⬇️
abci/client/socket_client.go	72.09% <0.00%> (-0.88%)	⬇️
state/execution.go	67.46% <0.00%> (-0.73%)	⬇️
p2p/pex/pex_reactor.go	79.67% <0.00%> (-0.62%)	⬇️
statesync/syncer.go	82.23% <0.00%> (-0.58%)	⬇️
proxy/multi_app_conn.go	47.66% <0.00%> (ø)
consensus/reactor.go	75.63% <0.00%> (+0.35%)	⬆️
light/client.go	61.71% <0.00%> (+0.45%)	⬆️
p2p/pex/addrbook.go	71.57% <0.00%> (+0.50%)	⬆️
... and 9 more