Fix documentation typos in `ofxClipPreferences`

[garyo]

Open Effects Proposal for Standard Change

Please read the contribution guidelines first.

Standard Change Workflow

• [x] Create proposal as issue (you're doing this now!)
• [x] Tag this issue with standard change tag
• [x] Identify subcommittee: at least one plug-in vendor, and at least one host
• [x] Discuss the idea in this issue
• [x] Write new or updated code and doc
• [x] Publish updates as a pull request (ideally on a feature/PROPOSAL-NAME branch)
  • [x] Make sure that PR references this issue number to keep them in sync
  • [x] Discuss and review code in the PR
  • [ ] Meet all requirements below for accepting PR
• [x] When subcommittee signs off and other members don't have any further review comments, maintainer merges PR to master which closes PR and issue

Requirements for accepting a standard change:

• [x] Header files updated
• [x] Documentation updated
• [x] Release notes added
• [x] Compatibility review completed
• [x] Working code demonstrated with at least one host and one plugin
• [x] At least two members sign off
• [x] No further changes requested from membership

Summary

Fix some doc typos is ofxClipPreferences.rst

Motivation

As a professional standard, doc should be free of typos.

Problem

Several typos exist on this page.

Impact

Doc only, no code change.

Documentation Impact

Docs should be rebuilt to test that this is done correctly.

Stakeholders

All

Discussion