python3: add rdepends for python3-idle

Add rdepends for python3-idle to fix below error:
 # /usr/bin/idle3 -h
 [snip]
 _tkinter.TclError: Can't find a usable init.tcl
 [snip]

Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>