wire: always set the QUIC bit for Version Negotiation packets

[marten-seemann]

Let's wait for a conclusion of the mailing list discussion before merging this: https://mailarchive.ietf.org/arch/msg/quic/oR4kxGKY6mjtPC1CZegY1ED4beg/

[codecov]

Codecov Report

Merging #3991 (50df246) into master (469a615) will increase coverage by 2.19%.
Report is 31 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3991      +/-   ##
==========================================
+ Coverage   82.86%   85.05%   +2.19%     
==========================================
  Files         146      147       +1     
  Lines       14729    15666     +937     
==========================================
+ Hits        12204    13324    +1120     
+ Misses       2025     1865     -160     
+ Partials      500      477      -23     

Files Changed	Coverage Δ
internal/wire/version_negotiation.go	92.31% <100.00%> (+0.64%)	⬆️

... and 20 files with indirect coverage changes

[marten-seemann]

Not a lot of discussion happening on the list.
I'm going to merge this PR since this is clearly allowed by the RFC. There's no harm to doing this, and it helps clients in certain situation.