of: unittest: Restore indentation in overlay_bad_add_dup_prop test

When updating the expected error messages for the
overlay_bad_add_dup_prop test, indentation of the EXPECT_END()
statements was accidentally changed.

Fixes: 29acfb65 ("of: unittest: kmemleak in duplicate property update")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/c9bd81b74b0a1ab394ac7ff8819e6fb032fe8ded.1690533838.git.geert+renesas@glider.beSigned-off-by: Rob Herring <robh@kernel.org>