Exclude appveyor config

[brettcannon]

Fixes #1236

This pull request:

• Has a title summarizes what is changing
• Includes a news entry file (remember to thank yourself!)
• Has unit tests & code coverage is not adversely affected (within reason)
• Works on all actively maintained versions of Python (e.g. Python 2.7 & the latest Python 3 release)
• Works on Windows 10, macOS, and Linux (e.g. considered file system case-sensitivity)

[DonJayamanne]

Thanks for sorting this, will review

[codecov]

Codecov Report

Merging #1287 into master will decrease coverage by 0.45%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1287      +/-   ##
==========================================
- Coverage   71.06%   70.61%   -0.46%     
==========================================
  Files         269      266       -3     
  Lines       12383    12284      -99     
  Branches     2190     2147      -43     
==========================================
- Hits         8800     8674     -126     
- Misses       3450     3487      +37     
+ Partials      133      123      -10

Impacted Files	Coverage Δ
src/client/common/configuration/service.ts	69.23% <0%> (-24.89%)	⬇️
src/client/debugger/mainV2.ts	56.3% <0%> (-19.73%)	⬇️
.../client/debugger/DebugClients/RemoteDebugClient.ts	17.64% <0%> (-17.36%)	⬇️
...client/debugger/DebugServers/LocalDebugServerV2.ts	60.86% <0%> (-13.05%)	⬇️
src/client/debugger/DebugClients/DebugFactory.ts	72.72% <0%> (-9.1%)	⬇️
...rc/client/debugger/DebugServers/BaseDebugServer.ts	66.66% <0%> (-6.67%)	⬇️
src/client/activation/analysis.ts	12.05% <0%> (-4.11%)	⬇️
src/client/common/net/socket/socketServer.ts	84.61% <0%> (-2.57%)	⬇️
src/client/debugger/PythonProcess.ts	48.75% <0%> (-2.5%)	⬇️
...c/client/debugger/DebugClients/LocalDebugClient.ts	51.96% <0%> (-2%)	⬇️
... and 10 more

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[brettcannon]

Thanks for the review!