Simplify tcp::Socket::can_recv

[smaeul]

This function does not actually care about the socket state, so there is no need to check it. The ability to immediately receive data only depends on there being something in the receive buffer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.45%. Comparing base (39cd44e) to head (4dab80c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1103      +/-   ##
==========================================
- Coverage   80.45%   80.45%   -0.01%     
==========================================
  Files          81       81              
  Lines       24461    24467       +6     
==========================================
+ Hits        19681    19685       +4     
- Misses       4780     4782       +2     

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