CompatHelper: bump compat for DataStructures to 0.19, (keep existing compat)

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This pull request changes the compat entry for the DataStructures package from ^0.17.0, ^0.18.0 to ^0.17.0, ^0.18.0, 0.19.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

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