Update CONTRIBUTING.md

Author: kassane

CONTRIBUTING.md

@@ -71,8 +71,8 @@ if (std.mem.eql(u8, op, "category/algorithm-name"))
 to test add:
 
 ```zig
-# runall.zig
+// runall.zig
 try runTest(allocator, "category/algorithm-name");
 ```
 
-**Note:** Do not change or modify the files (`build.zig` & `runall.zig`) without first suggesting it to the maintainers (open/issue proposal).
+**Note:** Do not change or modify the files (`build.zig` & `runall.zig`) without first suggesting it to the maintainers (open/issue proposal).