Update opt-in.html (#1813)

Updating opt in page to reflect updated language.

# Important

- If this PR updates a file in `content/en` with a `lastmod` field, it
**must** be updated.

- If this PR is a translation, please read
https://github.com/letsencrypt/website/blob/master/TRANSLATION.md first.

content/en/opt-in.html

@@ -1,14 +1,14 @@
 ---
-title: Sign up for the ISRG Newsletter
+title: Sign up for emails
 slug: opt-in
-date: 2024-11-18
+date: 2025-01-14
 should_display_prominent_newsletter_form: true
 ---
 
 <div class="text-left">
-    <p>ISRG's monthly newsletter recaps what we're up to and shares recent security and privacy news that caught our attention. </p>
+    <p>Sign up for emails from ISRG, the nonprofit behind Let's Encrypt. We’ll keep you informed about technical updates as well as other news about Let’s Encrypt and our sister projects, based on the preferences you choose.</p>
 
-    <p>By signing up for the Newsletter you agree to Let's Encrypt handling your information as described in our <a href="https://letsencrypt.org/privacy/">privacy policy</a>.</p>
+    <p>By signing up for emails you agree to Let's Encrypt and ISRG handling your information as described in our <a href="https://letsencrypt.org/privacy/">privacy policy</a>.</p>
 </div>
 
 <script>
@@ -32,4 +32,4 @@
 });
 
 
-</script>
+</script>