Fix links

Author: ntrogh

articles/playwright-testing/index.yml

@@ -25,7 +25,7 @@ landingContent:
           - text: What is Microsoft Playwright Testing?
             url: overview-what-is-microsoft-playwright-testing.md
           - text: Try Microsoft Playwright Testing for free
-            url: how-to-try-playwright-testing-free
+            url: how-to-try-playwright-testing-free.md
 
   # Card
   - title: Get started

articles/playwright-testing/toc.yml

@@ -9,7 +9,7 @@ items:
       href: overview-what-is-microsoft-playwright-testing.md
     - name: Try Microsoft Playwright Testing for free
       displayName: free trial, free, trial, try
-      href: how-to-try-playwright-testing-free
+      href: how-to-try-playwright-testing-free.md
 - name: Quickstarts
   expanded: true
   items: