Make Bob reply with a static lifetime

exercises/bob/example.rs

@@ -1,4 +1,4 @@
-pub fn reply(message: &str) -> &str {
+pub fn reply(message: &str) -> &'static str {
     if is_silence(message) { "Fine. Be that way!" }
     else if is_yelling(message) && is_question(message) { "Calm down, I know what I'm doing!" }
     else if is_yelling(message) { "Whoa, chill out!" }

exercises/bob/src/lib.rs

@@ -1,3 +1,3 @@
-pub fn reply(message: &str) -> &str {
-    unimplemented!("have Bob reply to the incoming message: {}", message)
-}
+pub fn reply(message: &str) -> &'static str {
+    unimplemented!("have Bob reply to the incoming message: {}", message)
+}