Remove FutureWarning for column suffixes

**Feature request**

crossmatch, merge_asof, and join give warnings on suffix methods, promising some future version will set the defaults. I think we're in the future now.

**Before submitting**
Please check the following:

- [ ] I have described the purpose of the suggested change, specifying what I need the enhancement to accomplish, i.e. what problem it solves.
- [ ] I have included any relevant links, screenshots, environment information, and data relevant to implementing the requested feature, as well as pseudocode for how I want to access the new functionality.
- [ ] If I have ideas for how the new feature could be implemented, I have provided explanations and/or pseudocode and/or task lists for the steps.