fix: Make GetShardLeaders skip retry on not loaded collection

[weiliu1031]

issue: #37532

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.55%. Comparing base (1304b40) to head (5fc2687).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #37684      +/-   ##
==========================================
- Coverage   80.57%   80.55%   -0.02%     
==========================================
  Files        1357     1357              
  Lines      190448   190463      +15     
==========================================
- Hits       153449   153434      -15     
- Misses      31588    31613      +25     
- Partials     5411     5416       +5     

Components	Coverage Δ
Client	61.25% <ø> (ø)
Core	68.07% <ø> (-0.01%)	⬇️
Go	83.18% <100.00%> (-0.02%)	⬇️

Files with missing lines	Coverage Δ
internal/proxy/lb_policy.go	98.06% <100.00%> (ø)

... and 27 files with indirect coverage changes

[czs007]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: czs007, weiliu1031

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