Fix RFC digital signature section link

The digital signature part of RFC 9116 is in § 2.3 (title: "Digital Signature").

There is no § 3.3 -- section 3 only goes up to 3.1.

Fix the link to work.

index.html

@@ -233,7 +233,7 @@ <h1 class="title">Step 1</h1>
 <section class="section">
     <div class="container">
         <h1 class="title" id="step-two">Step 2</h1>
-        <p>You are ready to go! Publish your security.txt file. If you want to give security researchers confidence that your security.txt file is authentic, and not planted by an attacker, consider <a target="_blank" rel="noopener" href="https://www.rfc-editor.org/rfc/rfc9116#section-3.3">digitally signing</a> the file with an OpenPGP cleartext signature.</p>
+        <p>You are ready to go! Publish your security.txt file. If you want to give security researchers confidence that your security.txt file is authentic, and not planted by an attacker, consider <a target="_blank" rel="noopener" href="https://www.rfc-editor.org/rfc/rfc9116#section-2.3">digitally signing</a> the file with an OpenPGP cleartext signature.</p>
         <div class="field">
           <div class="control">
             <textarea id="text-to-copy" class="textarea" readonly></textarea>