chore: Update docs for writing UI tests to use case for the test function name

Author: Muscraft

src/doc/contrib/src/tests/writing.md

@@ -171,7 +171,7 @@ use cargo_test_support::Project;
 use cargo_test_support::curr_dir;
 
 #[cargo_test]
-fn <name>() {
+fn case() {
     let project = Project::from_template(curr_dir!().join("in"));
     let project_root = project.root();
     let cwd = &project_root;