docs: grammar fix

Author: michaelKurowski

docs/content/4.sdk/2.getting-started/2.middleware-module.md

@@ -151,7 +151,7 @@ export const sdk = initSDK({
     errorHandler: ({ error, methodName, url, params, config, httpClient }) => {
       // Custom error handler
     },
-    cdnCacheBustingId: // git commit hash of the monorepo where both middleware and the storefront is located
+    cdnCacheBustingId: // git commit hash of the monorepo where both middleware and the storefront are located
   }),
 });
 ```