Better Dispose pattern for WebSocketConnection

[Shane32]

Follow-up to PR:

• Dispose of WebSocket when done with it #671

[codecov-commenter]

Codecov Report

Merging #673 (efa5737) into master (d4090a7) will decrease coverage by 0.55%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #673      +/-   ##
==========================================
- Coverage   55.65%   55.09%   -0.56%     
==========================================
  Files          64       64              
  Lines        1592     1590       -2     
  Branches      158      158              
==========================================
- Hits          886      876      -10     
- Misses        652      660       +8     
  Partials       54       54              

Impacted Files	Coverage Δ
...riptions.WebSockets/GraphQLWebSocketsMiddleware.cs	86.48% <0.00%> (ø)
...ts.Subscriptions.WebSockets/WebSocketConnection.cs	0.00% <0.00%> (ø)
....Subscriptions.Abstractions/LogMessagesListener.cs	0.00% <0.00%> (-40.00%)	⬇️
src/Core/Extensions/ServiceCollectionExtensions.cs	56.52% <0.00%> (-26.09%)	⬇️

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