Make it clear in PR template that not all changes will necessitate docs and README updates.

Signed-off-by: David Jackson <58445547+daj-code@users.noreply.github.com>

Author: daj-code

.github/PULL_REQUEST_TEMPLATE.md

@@ -15,6 +15,6 @@ Anything you think will be useful for reviewers.
 These aren't hard requirements, just guidelines
 
 - [ ] New/modified Rust code formatted with `cargo fmt`
-- [ ] Documentation and `README.md` updated for this change
+- [ ] Documentation and `README.md` updated for this change, if necessary
 - [ ] `CHANGELOG.md` updated for this change