Adds desable info to instructions (#16924)

Author: angelampcosta

src/content/docs/speed/optimization/content/speculation.mdx

@@ -78,11 +78,11 @@ Speculation is available in Cloudflare’s **Speed** tab of the dashboard and al
 
 <Tabs syncKey="dashPlusAPI"> <TabItem label="Dashboard">
 
-To enable **Prefetch URLs** in the dashboard:
+To enable or disable **Prefetch URLs** in the dashboard:
 
 1. Log in to your [Cloudflare account](https://dash.cloudflare.com), select your account and go to a specific domain.
 2. Go to **Speed** > **Optimization** > **Content Optimization**.
-3. Enable **Speculation**.
+3. Toggle **Speculation** to **On** or **Off**.
 
 </TabItem> <TabItem label="API">