docs: fix removed anchor (#2456)

* fix: removed anchor

* docs: Update src/api/reactivity-core.md

---------

Co-authored-by: Ben Hong <ben@bencodezen.io>

Author: jay-es

src/api/reactivity-core.md

@@ -40,7 +40,7 @@ Takes an inner value and returns a reactive and mutable ref object, which has a
   ```
 
 - **See also**
-  - [Guide - Reactive Variables with `ref()`](/guide/essentials/reactivity-fundamentals#reactive-variables-with-ref)
+  - [Guide - Reactivity Fundamentals with `ref()`](/guide/essentials/reactivity-fundamentals#ref)
   - [Guide - Typing `ref()`](/guide/typescript/composition-api#typing-ref) <sup class="vt-badge ts" />
 
 ## computed() {#computed}