Update Exercises Directory Names to Reflect Order

exercises/00_intro/intro2.rs

@@ -0,0 +1,12 @@
+// intro2.rs
+//
+// Make the code print a greeting to the world.
+//
+// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+fn main() {
+    println!("Hello {}!");
+}