Fix micros (optional) limit in and_hms_micro_opt

[qrilka]

Thanks for contributing to chrono!

If your feature is semver-compatible, please target the main branch;
for semver-incompatible changes, please target the 0.5.x branch.

Please consider adding a test to ensure your bug fix/feature will not break in the future.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.78%. Comparing base (f129a8b) to head (2ff363a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1584   +/-   ##
=======================================
  Coverage   91.78%   91.78%           
=======================================
  Files          37       37           
  Lines       18208    18208           
=======================================
  Hits        16713    16713           
  Misses       1495     1495           

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[djc]

Thanks!