Remove appveyor

[seladb]

Appveyor only runs the VS 2017 build which we don't support anymore.
Regardless, it wasn't running in the last 9 months 😕 : https://ci.appveyor.com/project/seladb/pcapplusplus

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (36913c3) 82.40% compared to head (06cad46) 82.41%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1266   +/-   ##
=======================================
  Coverage   82.40%   82.41%           
=======================================
  Files         161      161           
  Lines       20738    20738           
  Branches     7839     7839           
=======================================
+ Hits        17090    17092    +2     
- Misses       2978     2994   +16     
+ Partials      670      652   -18     

Flag	Coverage Δ
alpine317	72.22% <ø> (ø)
centos7	74.33% <ø> (ø)
fedora37	72.23% <ø> (ø)
macos-11	61.11% <ø> (ø)
macos-12	61.17% <ø> (ø)
macos-ventura	61.19% <ø> (-0.02%)	⬇️
mingw32	70.09% <ø> (ø)
mingw64	70.09% <ø> (-0.03%)	⬇️
npcap	83.20% <ø> (ø)
ubuntu1804	74.80% <ø> (ø)
ubuntu2004	72.99% <ø> (ø)
ubuntu2204	72.06% <ø> (ø)
ubuntu2204-icpx	59.11% <ø> (+0.04%)	⬆️
unittest	82.41% <ø> (+<0.01%)	⬆️
windows-2019	83.21% <ø> (ø)
windows-2022	83.22% <ø> (ø)
winpcap	83.18% <ø> (ø)
xdp	58.67% <ø> (ø)
zstd	73.57% <ø> (-0.03%)	⬇️

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