Update technote with new wetlands algorithms

(Please see our [contribution guidelines for documentation](https://escomp.github.io/CTSM/users_guide/working-with-documentation/docs-intro.html#contribution-guidelines).)

### What sort(s) of documentation issue is this?
- [x] Something is missing.
- [x] Something is (or might be) incorrect or outdated.
- [ ] Something is confusing.
- [ ] Something is broken.

### What part(s) of the documentation does this concern?
- [x] [Technical Note](https://escomp.github.io/CTSM/tech_note/index.html) (science and design of the model)
- [ ] [User's Guide](https://escomp.github.io/CTSM/users_guide/index.html) (using the model and related tools)
- [ ] Somewhere else (e.g., README file, tool help text, or code comment): _Please specify_
- [ ] I don't know

### Describe the issue
The wetlands branch is getting merged to master as of ctsm5.4.056, so the Technote needs updating.

### Additional context (optional)
Wetlands are currently mentioned in [section 2.7.2.2](https://escomp.github.io/CTSM//tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html#surface-water-storage).

@swensosc the replacement documentation may go in the same section or you may prefer a different organization.