Remove registration fallback code. (#15405)

The registration fallback is broken and unspecced. This removes it
since there is no plan to spec it.

Note that this does not modify the login fallback code.

changelog.d/15405.removal

@@ -0,0 +1 @@
+Remove the broken, unspecced registration fallback. Note that the *login* fallback is unaffected by this change.

synapse/res/templates/recaptcha.html

@@ -3,7 +3,11 @@
 
 {% block header %}
 <script src="https://www.recaptcha.net/recaptcha/api.js" async defer></script>
-<link rel="stylesheet" href="/_matrix/static/client/register/style.css">
+<style type="text/css">
+  .g-recaptcha div {
+    margin: auto;
+  }
+</style>
 <script>
 function captchaDone() {
     document.getElementById('registrationForm').submit(); 

synapse/res/templates/registration_token.html

@@ -1,12 +1,8 @@
 {% extends "_base.html" %}
 {% block title %}Authentication{% endblock %}
 
-{% block header %}
-<link rel="stylesheet" href="/_matrix/static/client/register/style.css">
-{% endblock %}
-
 {% block body %}
-<form id="registrationForm" method="post" action="{{ myurl }}">
+<form method="post" action="{{ myurl }}">
     <div>
         {% if error is defined %}
             <p class="error"><strong>Error: {{ error }}</strong></p>

synapse/res/templates/style.css

@@ -27,3 +27,7 @@ body {
     h3 { font-size: .85rem; }
     h4 { font-size: .8rem; }
 }
+
+.error {
+    color: red;
+}

synapse/res/templates/terms.html

@@ -2,7 +2,12 @@
 {% block title %}Authentication{% endblock %}
 
 {% block header %}
-<link rel="stylesheet" href="/_matrix/static/client/register/style.css">
+<style type="text/css">
+  #registrationForm input {
+    display: block;
+    margin: auto;
+  }
+</style>
 {% endblock %}
 
 {% block body %}