Isn't possible to override theme as path is explicitly set for template
Add a copy of the template `field--paragraphs-grid-formatter.html.twig` into your own theme template directory.
I understand the motivation for providing the hardcoded path (otherwise, the module can't easily supply a TWIG template within its own codebase).
Perhaps some conditional logic could be introduced to allow template overrides?
For now, I'm adding a patch to remove this.
Needs review
1.0
Code