conf-notes: remove reference to adt-installer

As adt-installer is not supported anymore in 2.1,
removed the reference to it from "Common targets".

[YOCTO #9256]

(From meta-yocto rev: b4b516f69da3127d3861116d77373f96f8257d50)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-poky/conf/conf-notes.txt

@@ -2,7 +2,6 @@ Common targets are:
     core-image-minimal
     core-image-sato
     meta-toolchain
-    adt-installer
     meta-ide-support
 
 You can also run generated qemu images with a command like 'runqemu qemux86'