transport: Remove unused return value from connect()

[twz123]

See:

• clientconn: Wait for all goroutines on close #8666 (comment)

RELEASE NOTES: none

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.35%. Comparing base (4046676) to head (08d9a68).
⚠️ Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8787      +/-   ##
==========================================
- Coverage   83.42%   83.35%   -0.07%     
==========================================
  Files         418      418              
  Lines       32897    32896       -1     
==========================================
- Hits        27443    27422      -21     
- Misses       4069     4082      +13     
- Partials     1385     1392       +7     

Files with missing lines	Coverage Δ
clientconn.go	90.43% <100.00%> (-0.25%)	⬇️

... and 26 files with indirect coverage changes

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[mbissa]

The title should be changed to transport instead of clientconn