fix(traits1): rename test functions to snake case (#854)

Co-authored-by: zhangshaozhi <zhangshaozhi@ZhangshaozhideMacBook-Pro.local>

exercises/traits/traits1.rs

@@ -29,12 +29,12 @@ mod tests {
     use super::*;
 
     #[test]
-    fn is_FooBar() {
+    fn is_foo_bar() {
         assert_eq!(String::from("Foo").append_bar(), String::from("FooBar"));
     }
 
     #[test]
-    fn is_BarBar() {
+    fn is_bar_bar() {
         assert_eq!(
             String::from("").append_bar().append_bar(),
             String::from("BarBar")