fix: use proper bulma styles for markdown content

cf. https://bulma.io/documentation/elements/content/

src/wuttaweb/templates/batch/view.mako

@@ -1,19 +1,6 @@
 ## -*- coding: utf-8; -*-
 <%inherit file="/master/view.mako" />
 
-<%def name="extra_styles()">
-  ${parent.extra_styles()}
-  <style>
-
-    ## TODO: should we do something like this site-wide?
-    ## (so far this is the only place we use markdown)
-    .markdown p {
-        margin-bottom: 1.5rem;
-    }
-
-  </style>
-</%def>
-
 <%def name="tool_panels()">
   ${parent.tool_panels()}
   ${self.tool_panel_execution()}
@@ -65,7 +52,7 @@
                     <p class="block has-text-weight-bold">
                       What will happen when this batch is executed?
                     </p>
-                    <div class="markdown">
+                    <div class="content">
                       ${execution_described|n}
                     </div>
                     ${h.form(master.get_action_url('execute', batch), ref='executeForm')}