Update writing-tests.mdx

Author: Bilogweb3

src/pages/cw-multi-test/getting-started/writing-tests.mdx

@@ -49,7 +49,7 @@ Luckily, `clippy` reports no issues for the **counter** smart contract.
 ## Preparing the directory structure for tests
 
 Before we start writing tests, we need to set up the directories and files for the test cases. The
-final directory and file structure is shown below.
+final directory and file structure are shown below.
 
 ```ansi showLineNumbers {7-11} filename="counter (directory)"
 .