Added semicolons to make the code snippet syntactically correct (#11303)

Author: tobias-wilfert

platform-includes/performance/add-spans-example/rust.mdx

@@ -16,17 +16,17 @@ fn perform_checkout() {
         "validating shopping cart",
     );
 
-    validate_shopping_cart() //Some long process, maybe a sync http request.
+    validate_shopping_cart(); //Some long process, maybe a sync http request.
 
     validation_span.finish();
 
     // Process the order
     let process_span = transaction.start_child(
         "process",
         "processing shopping cart",
-    )
+    );
 
-    process_shopping_cart() //Another time consuming process.
+    process_shopping_cart(); //Another time consuming process.
 
     process_span.finish();