Fix #11308 : Remove dependency on jquery on reCAPTCHA page (#14672)

Author: JeyRathnam

changelog.d/14672.misc

@@ -0,0 +1 @@
+Remove dependency on jQuery on reCAPTCHA page.

synapse/res/templates/recaptcha.html

@@ -3,11 +3,10 @@
 
 {% block header %}
 <script src="https://www.recaptcha.net/recaptcha/api.js" async defer></script>
-<script src="//code.jquery.com/jquery-1.11.2.min.js"></script>
 <link rel="stylesheet" href="/_matrix/static/client/register/style.css">
 <script>
 function captchaDone() {
-    $('#registrationForm').submit();
+    document.getElementById('registrationForm').submit(); 
 }
 </script>
 {% endblock %}