Update Exercises Directory Names to Reflect Order

exercises/01_variables/variables2.rs

@@ -0,0 +1,15 @@
+// variables2.rs
+//
+// Execute `rustlings hint variables2` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+fn main() {
+    let x;
+    if x == 10 {
+        println!("x is ten!");
+    } else {
+        println!("x is not ten!");
+    }
+}