help: Move span to new line for channel-permissions.

Before, the `span` opening tag was split between two lines. This
led to `[@mdx-js/rollup]` throwing an error on the build step saying
`Expected a closing tag for <span> before the end of paragraph`.
This is a preparatory commit for the migration to use starlight
for help center docs.

help/channel-permissions.md

@@ -81,7 +81,8 @@ administrator can access private channel messages:
 
 <span class="legend_symbol">&#9726;</span><span class="legend_label">If subscribed to the channel</span>
 
-<span class="legend_symbol">&#10038;</span><span class="legend_label">
+<span class="legend_symbol">&#10038;</span>
+<span class="legend_label">
 Configurable. See [Channel posting policy](/help/channel-posting-policy),
 [Configure who can add users][add-users], and
 [Configure who can remove users][remove-users]
@@ -111,7 +112,8 @@ for details.
 
 <span class="legend_symbol">&#9726;</span><span class="legend_label">If subscribed to the channel</span>
 
-<span class="legend_symbol">&#10038;</span><span class="legend_label">
+<span class="legend_symbol">&#10038;</span>
+<span class="legend_label">
 Configurable, but at minimum must be subscribed to the channel.
 See [Channel posting policy](/help/channel-posting-policy),
 [Configure who can add users][add-users], and