Update contributing (#6725)

Mikayla Maki created 

[[PR Description]]

Release Notes:

- (Added|Fixed|Improved) ...
([#<public_issue_number_if_exists>](https://github.com/zed-industries/zed/issues/<public_issue_number_if_exists>)).

Change summary

CONTRIBUTING.md | 1 +
1 file changed, 1 insertion(+)

Detailed changes

CONTRIBUTING.md 🔗 

@@ -37,6 +37,7 @@ We plan to set aside time each week to pair program with contributors on promisi
 - Add test coverage and documentation
 - Choose tasks that align with our roadmap
 - Pair with us and watch us code to learn the codebase
+- Low effort PRs, such as those that just re-arrange syntax, won't be merged without a compelling justification
 
 ## Bird-eye's view of Zed