sdk-desktop-icon-devhelp: Drop leftovers from before the split

The sdk-desktop-icon-devhelp overlay still contained the whole contents
of the old sdk overlay before we split it out.

It now only contains the /etc/skel/Desktop/devhelp.desktop file.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

overlays/sdk-desktop-icon-devhelp/etc/lightdm/lightdm.conf.d/autologin.conf

-[Seat:*]
-user-session=xfce
-autologin-user=user
-autologin-user-timeout=0

overlays/sdk-desktop-icon-devhelp/etc/skel/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-desktop.xml

-<?xml version="1.0" encoding="UTF-8"?>
-
-<channel name="xfce4-desktop" version="1.0">
-  <property name="backdrop" type="empty">
-    <property name="screen0" type="empty">
-      <property name="monitor0" type="empty">
-        <property name="image-path" type="empty"/>
-        <property name="image-show" type="empty"/>
-        <property name="color1" type="empty"/>
-        <property name="workspace0" type="empty">
-          <property name="color-style" type="int" value="0"/>
-          <property name="color1" type="array">
-            <value type="uint" value="58136"/>
-            <value type="uint" value="58136"/>
-            <value type="uint" value="58136"/>
-            <value type="uint" value="65535"/>
-          </property>
-          <property name="image-style" type="int" value="5"/>
-          <property name="last-image" type="string" value="/usr/share/sac-sdk/wallpapers/apertis-desktop.png"/>
-        </property>
-      </property>
-    </property>
-  </property>
-</channel>
-

overlays/sdk-desktop-icon-devhelp/etc/skel/.config/xfce4/xfconf/xfce-perchannel-xml/xsettings.xml

-<?xml version="1.0" encoding="UTF-8"?>
-
-<channel name="xsettings" version="1.0">
-  <property name="Net" type="empty">
-    <property name="ThemeName" type="string" value="Xfce-4.6"/>
-  </property>
-</channel>

overlays/sdk-desktop-icon-devhelp/etc/skel/Desktop/eclipse.desktop

-[Desktop Entry]
-Type=Application
-Name=Eclipse
-Comment=Eclipse Integrated Development Environment
-Icon=eclipse
-Exec=eclipse
-Terminal=false
-Categories=Development;IDE;Java;

overlays/sdk-desktop-icon-devhelp/lib/systemd/system/opt-sysroot.mount

-[Unit]
-Description=Mount points for sysroots
-Before=local-fs.target
-
-[Mount]
-What=/home/sysroot
-Where=/opt/sysroot
-Type=none
-Options=rbind
-
-[Install]
-WantedBy=default.target