meta-facebook: remove excess override syntaxes

When a bbappend file is already in a meta-machine layer, there is no
reason for extra ":machine" override syntax usage.  Remove them all.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I610e72633adb5bc36b63fe2b727e394c61070185
diff --git a/meta-facebook/meta-greatlakes/recipes-fb/ipmi/fb-ipmi-oem_%.bbappend b/meta-facebook/meta-greatlakes/recipes-fb/ipmi/fb-ipmi-oem_%.bbappend
index e70f2a1..1a50050 100644
--- a/meta-facebook/meta-greatlakes/recipes-fb/ipmi/fb-ipmi-oem_%.bbappend
+++ b/meta-facebook/meta-greatlakes/recipes-fb/ipmi/fb-ipmi-oem_%.bbappend
@@ -1 +1 @@
-EXTRA_OEMESON:append:greatlakes=" -Dpost-code-bytes=${POST_CODE_BYTES}"
+EXTRA_OEMESON:append =" -Dpost-code-bytes=${POST_CODE_BYTES}"