meta-phosphor: prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I588025b614416c43aa2d053765ab53bacf890cb5
diff --git a/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb b/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
index e4f955f..494b06c 100644
--- a/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
+++ b/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
@@ -51,4 +51,4 @@
 
 # The shadow recipe provides the binaries(like useradd, usermod) needed by the
 # phosphor-user-manager.
-ROOTFS_RO_UNNEEDED_remove = "shadow"
+ROOTFS_RO_UNNEEDED:remove = "shadow"