Use doc layout instead of sidebar layout

There appears to be no strong reason that these pages are using a
different layout, and having this separate layout significantly
increases the ongoing doc maintenance burden.

developer/general/gsoc.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-layout: sidebar
+layout: doc
 permalink: /gsoc/
 redirect_from:
 - /GSoC/

developer/general/gsod.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-layout: sidebar
+layout: doc
 permalink: /gsod/
 ref: 242
 title: Google Season of Docs

developer/general/join.md

@@ -1,12 +1,11 @@
 ---
 lang: en
-layout: sidebar
+layout: doc
 permalink: /join/
 ref: 26
 title: Join
 ---
 
-
 The Qubes OS Project does not currently have any open positions.
 This page will be updated when open positions become available.
 In the meantime, there are many different ways you can [contribute to the Qubes OS project](/doc/contributing/).

introduction/code-of-conduct.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-layout: default
+layout: doc
 permalink: /code-of-conduct/
 ref: 118
 title: Code of Conduct

introduction/support.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-layout: sidebar
+layout: doc
 permalink: /support/
 redirect_from:
 - /help/

user/downloading-installing-upgrading/download-mirrors.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-layout: sidebar
+layout: doc
 permalink: /downloads/mirrors/
 ref: 148
 title: Download Mirrors