Docs: Fix HTML5 for Install Logos (#1397)

With the update tot HTML5 in docutils, we need to modernize our CSS
code that does fancy logos in the user install section.

Author: ax3l

docs/source/install/install.rst

@@ -6,7 +6,7 @@ Installation
 .. raw:: html
 
    <style>
-   .rst-content .section>img {
+   .rst-content section>img {
        width: 30px;
        margin-bottom: 0;
        margin-top: 0;