tweak

CONTRIBUTING.md

 
 Also, please ensure your pull request adheres to the following guidelines:
 
-* Your suggestion is not a duplicate or has been previously rejected, otherwise it will be closed.
+* Your suggestion hasn't been previously rejected or is a duplicate, otherwise it will be closed.
 * Write a meaningful pull request description which includes a link to the project.
 * Adheres to the following Markdown format: `[LIBRARY](LINK) - DESCRIPTION.`
 * Your description is short, clear, unbiased, and doesn't contain any jargon.