remove += from _append

No need to use _append and +=

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: Ic1e1f685be9a901b33d7d6d43938677b975c6e0a
diff --git a/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend b/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend
index db95cda..3c658ae 100644
--- a/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend
+++ b/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend
@@ -1,6 +1,6 @@
 FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
 SRC_URI_append_ibm-ac-server = " file://TPMEnable-default-true.override.yml"
-SRC_URI_append_ibm-ac-server += " file://ClearHostSecurityKeys-default-zero.override.yml"
+SRC_URI_append_ibm-ac-server = " file://ClearHostSecurityKeys-default-zero.override.yml"
 SRC_URI_append_mihawk = " file://TPMEnable-default-true.override.yml"
 SRC_URI_append = " file://ibm_settings.override.yml"
 SRC_URI_append_rainier = " file://HypervisorInterface-default-rainier.override.yml"