fix(sse): prevent onClosed from firing twice in EventStream

[joshmossas]

Fixes issue where onClosed always fires twice when using Server Sent Events.

The following changes were made to fix the issue:

• remove redundant event.node.res.on('close') hook in onClosed method

The following changes were made to related documentation:

• Remove redundant eventStream.close() invocation from ./examples/server-sent-events.ts
• Remove redundant eventStream.close() invocation from ./docs/1.guide/6.websockets.md
• Remove redundant eventStream.close() invocation from ./tests/sse.test.ts

eventStream.close() doesn't need to be called in onClosed by default because it is automatically handled when autoclose is set to true

🔗 Linked issue

Fixes #703

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 79.73%. Comparing base (a58d7c9) to head (4fb9e71).
Report is 64 commits behind head on main.

Files	Patch %	Lines
examples/server-sent-events.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #704      +/-   ##
==========================================
+ Coverage   77.83%   79.73%   +1.89%     
==========================================
  Files          47       53       +6     
  Lines        4286     5294    +1008     
  Branches      611      674      +63     
==========================================
+ Hits         3336     4221     +885     
- Misses        933     1055     +122     
- Partials       17       18       +1     

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[joshmossas]

@pi0 Just curious what was the reason you marked this PR as a draft. I just wanted to check and see if I needed to change something on my end.