Update index.mdx

Author: robin-norwood

website/docs/plugin/framework/functions/index.mdx

@@ -3,7 +3,7 @@ page_title: Provider-defined functions overview
 description: >-
   Provider-defined functions expose logic beyond Terraform's built-in functions
   that practitioners can use to simplify Terraform configurations. Learn how the
-  provider framework can help you implement provider-defined functions.
+  plugin framework can help you implement provider-defined functions.
 ---