fix(convert): Whitespace issue in default RevealJS template (#442)

* Fix whitespace issue in RevealJS template

* Edit changelog

docs/source/_static/template.html

@@ -32,7 +32,7 @@
               data-background-video="{{ file }}"
               {% if loop.index == 1 and outer_loop.index == 1 -%}
                 data-background-video-muted
-              {%- endif -%}
+              {%- endif %}
               {% if slide_config.loop -%}
                 data-background-video-loop
               {%- endif -%}