dev-manual: pass False to d.getVar() for devpyshell example

In the example in section 3.9, the call to d.getVar() needs to have
the additional argument of "False" so that the output is not expanded.

(From yocto-docs rev: ae364e76a322278e7fe37aeecaa5e854d0a0efee)

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Reviewed-by: Quentin Schulz <foss@0leil.net>
Tested-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/common-tasks.rst

@@ -3486,7 +3486,7 @@ functions::
 
    pydevshell> d.getVar("STAGING_DIR")
    '/media/build1/poky/build/tmp/sysroots'
-   pydevshell> d.getVar("STAGING_DIR")
+   pydevshell> d.getVar("STAGING_DIR", False)
    '${TMPDIR}/sysroots'
    pydevshell> d.setVar("FOO", "bar")
    pydevshell> d.getVar("FOO")