Remove spurious action button on 'create workflow task' view (#7762)

* Remove spurious action button on 'create workflow task' view

Fixes #7758. 1fe36d2597 fixed the generic base template to stop the `action_url` from leaking into the header, but create_task.html bypasses the base template so needs the fix applying separately.

* Remove spurious action button on 'edit workflow task' view

* Remove spurious action button on 'edit workflow' view

wagtail/admin/templates/wagtailadmin/workflows/create_task.html

@@ -22,7 +22,7 @@
 
 {% block content %}
 
-    {% include "wagtailadmin/shared/header.html" with title=view.page_title icon=view.header_icon merged=1 %}
+    {% include "wagtailadmin/shared/header.html" with title=view.page_title icon=view.header_icon merged=1 only %}
 
     <form action="{{ view.get_add_url }}" enctype="multipart/form-data" method="POST" novalidate>
         {% csrf_token %}

wagtail/admin/templates/wagtailadmin/workflows/edit.html

@@ -26,7 +26,7 @@
 {% endblock %}
 
 {% block content %}
-    {% include "wagtailadmin/shared/header.html" with title=view.page_title subtitle=object.name icon=view.header_icon merged=1 %}
+    {% include "wagtailadmin/shared/header.html" with title=view.page_title subtitle=object.name icon=view.header_icon merged=1 only %}
 
     <form action="{% block form_action %}{{ view.edit_url }}{% endblock %}"{% if is_multipart %} enctype="multipart/form-data"{% endif %} method="POST" novalidate>
         {% csrf_token %}

wagtail/admin/templates/wagtailadmin/workflows/edit_task.html

@@ -23,7 +23,7 @@
 {% endblock %}
 
 {% block content %}
-    {% include "wagtailadmin/shared/header.html" with title=view.page_title subtitle=object.name icon=view.header_icon merged=1 %}
+    {% include "wagtailadmin/shared/header.html" with title=view.page_title subtitle=object.name icon=view.header_icon merged=1 only %}
 
     <form action="{{ view.edit_url }}" enctype="multipart/form-data" method="POST" novalidate>
         {% csrf_token %}