chore: add \n to matrix generation (#6041)

preventing those "empty" PRs: 
#6039

## Checklist

- [ ] Title matches [Winglang's style guide](https://www.winglang.io/contributing/start-here/pull_requests#how-are-pull-request-titles-formatted)
- [ ] Description explains motivation and solution
- [ ] Tests added (always)
- [ ] Docs updated (only required for features)
- [ ] Added `pr/e2e-full` label if this feature requires end-to-end testing

*By submitting this pull request, I confirm that my contribution is made under the terms of the [Wing Cloud Contribution License](https://github.com/winglang/wing/blob/main/CONTRIBUTION_LICENSE.md)*.

tools/compatibility-matrix-automation/src/matrix-automation.ts

@@ -42,7 +42,7 @@ export function updateMatrix(outFolderPath: string, matrixPath = MATRIX_PATH) {
     }
   }
 
-  writeFileSync(MATRIX_PATH, JSON.stringify(matrix, null, 2));
+  writeFileSync(MATRIX_PATH, `${JSON.stringify(matrix, null, 2)}\n`);
 }
 
 export function updateMatrixFromFile(