Fix shifted line in FFox

ws/Docbook/CustomLayer/slide/reveal.css.patch

@@ -15,15 +15,6 @@ diff -Naur css.orig/reveal.css css/reveal.css
  /*!
   * reveal.js
   * http://lab.hakim.se/reveal-js
-@@ -26,7 +36,7 @@
-   border: 0;
-   font-size: 100%;
-   font: inherit;
--  vertical-align: baseline; }
-+  vertical-align: top; }
- 
- .reveal article, .reveal aside, .reveal details, .reveal figcaption, .reveal figure,
- .reveal footer, .reveal header, .reveal hgroup, .reveal menu, .reveal nav, .reveal section {
 diff -Naur css.orig/theme/serif.css css/theme/serif.css
 --- css.orig/theme/serif.css	2018-05-30 16:09:42.483334660 +0200
 +++ css/theme/serif.css	2018-05-30 16:07:49.037908476 +0200