tests: fix overridable()

Tested:
cargo test -p structopt --test rename_all_env

Signed-off-by: Changyuan Lyu <[email protected]>
diff --git a/tests/rename_all_env.rs b/tests/rename_all_env.rs
index ad5776b..24cba2e 100644
--- a/tests/rename_all_env.rs
+++ b/tests/rename_all_env.rs
@@ -42,5 +42,5 @@
 
     let help = get_help::<BehaviorModel>();
     assert!(help.contains("[env: be-nice=]"));
-    assert!(help.contains("[env: BeAgressive=]"));
+    assert!(help.contains("[env: BeAggressive=]"));
 }