contrib.gdpopt: Adding missing import for gdpopt.enumerate

[emma58]

Fixes # .

Summary/Motivation:

One-line fix: We weren't registering gdpopt.enumerate when the rest of gdpopt is imported. This will make it so that now we are.

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (85b63ab) 88.26% compared to head (af2abcf) 88.26%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3105   +/-   ##
=======================================
  Coverage   88.26%   88.26%           
=======================================
  Files         832      832           
  Lines       92385    92386    +1     
=======================================
+ Hits        81544    81545    +1     
  Misses      10841    10841           

Flag	Coverage Δ
linux	86.02% <100.00%> (+<0.01%)	⬆️
osx	75.54% <100.00%> (+<0.01%)	⬆️
other	86.20% <100.00%> (+<0.01%)	⬆️
win	83.43% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.