Improve wording of 'unpublish subpages' checkbox and make it an actual label

wagtail/wagtailadmin/static_src/wagtailadmin/scss/components/_forms.scss

@@ -42,6 +42,15 @@ label,
     }
 }
 
+.plain-checkbox-label {
+    // cancel heavy / floated label styles, for labels that should appear inline against checkboxes
+
+    float: none;
+    color: inherit;
+    font-weight: inherit;
+    font-size: inherit;
+}
+
 input,
 textarea,
 select,

wagtail/wagtailadmin/templates/wagtailadmin/pages/confirm_unpublish.html

@@ -17,11 +17,11 @@
                         <div class="field-content">
                             <div class="input">
                                 <input id="id_include_descendants" name="include_descendants" type="checkbox">
-                                <span>{% blocktrans count counter=live_descendant_count %}
-                    This will also unpublish one more subpage.
+                                <label for="id_include_descendants" class="plain-checkbox-label">{% blocktrans count counter=live_descendant_count %}
+                    This page has one subpage. Unpublish this too
                 {% plural %}
-                    This will also unpublish {{ live_descendant_count }} more subpages.
-                {% endblocktrans %}</span>
+                    This page has {{ live_descendant_count }} subpages. Unpublish these too
+                {% endblocktrans %}</label>
                             </div>
                         </div>
                     </div>