Add proxsuite to global pinnings

[olivier-roussel]

As initiated in this discussion, proxsuite is required by several packages on conda-forge. Adding proxsuite to global pinning would make easier the maintenance of packages that depends on it, as this would be automated at each version increase.
Just for clarification, could you confirm that the global pinning is automatically updated when a new version of the proxsuite conda package is updated ?
What do you think also about this @conda-forge/proxsuite ?

[hmaarrfk]

Anything with a run_export should be added to the global pinnins.

please do the following:

1. create a migrator file with the new pinning
2. Add a note in it to add it to the global pinnings once migration complete
3. cross reference this issue in your pull request.