[Fundamentals] Update free-plan.mdx

Hey team, could we use "Free"  here as in the plan's name?

Author: nenizera

src/content/docs/fundamentals/concepts/free-plan.mdx

@@ -1,6 +1,6 @@
 ---
 pcx_content_type: concept
-title: Our free plan
+title: Our Free plan
 sidebar:
   order: 4
 head: