Remove back link from 404 error page (#23222967)

I've kept it for 400/403/500/csrffail for now, because they also have a
"try again" link. Yes, both things have browser buttons, but they make
it a *little* clearer to technical users what one could to next, and
especially on csrffail, "step back" is always possible and possibly actually
helpful.

src/pretix/base/forms/widgets.py

@@ -42,8 +42,6 @@ from django.utils.html import escape
 from django.utils.timezone import get_current_timezone, now
 from django.utils.translation import gettext_lazy as _
 
-from pretix.helpers.format import PlainHtmlAlternativeString
-
 
 def replace_arabic_numbers(inp):
     if not isinstance(inp, str):
@@ -63,18 +61,11 @@ def replace_arabic_numbers(inp):
     return inp.translate(table)
 
 
-def format_placeholder_help_text(placeholder_name, sample_value):
-    if isinstance(sample_value, PlainHtmlAlternativeString):
-        sample_value = sample_value.plain
-    title = (_("Sample: %s") % sample_value) if sample_value else ""
-    return ('<button type="button" class="content-placeholder" title="%s">{%s}</button>' % (escape(title), escape(placeholder_name)))
-
-
 def format_placeholders_help_text(placeholders, event=None):
     placeholders = [(k, v.render_sample(event) if event else v) for k, v in placeholders.items()]
     placeholders.sort(key=lambda x: x[0])
     phs = [
-        format_placeholder_help_text(k, v)
+        '<button type="button" class="content-placeholder" title="%s">{%s}</button>' % (escape(_("Sample: %s") % v) if v else "", escape(k))
         for k, v in placeholders
     ]
     return _('Available placeholders: {list}').format(

src/pretix/base/templates/404.html

@@ -8,9 +8,6 @@
         <h1>{% trans "Not found" %}</h1>
         <p>{% trans "I'm afraid we could not find the the resource you requested." %}</p>
         <p>{{ exception }}</p>
-        <p class="links">
-            <a id='goback' href='#'>{% trans "Take a step back" %}</a>
-        </p>
         {% if request.user.is_staff and not staff_session %}
             <form action="{% url 'control:user.sudo' %}?next={{ request.path|add:"?"|add:request.GET.urlencode|urlencode }}" method="post">
                 <p>

src/pretix/presale/templates/pretixpresale/event/resend_link.html

@@ -1,14 +1,14 @@
 {% extends "pretixpresale/event/base.html" %}
 {% load i18n %}
 {% load bootstrap3 %}
-{% block title %}{% trans "Resend order links" %}{% endblock %}
+{% block title %}{% trans "Resend order link" %}{% endblock %}
 {% block custom_header %}
     {{ block.super }}
     <meta name="robots" content="noindex, nofollow">
 {% endblock %}
 {% block content %}
     <h2>
-        {% trans "Resend order links" %}
+        {% trans "Resend order link" %}
     </h2>
     <p>
         {% blocktrans trimmed %}