meta-ampere: remove BBLAYERS_NON_REMOVABLE

This variable hasn't existed in upstream poky since 2016.  See
commit d06c7b8ce6249529de0bde0a568c0658b7148bf4 from their repository.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8c832b1f4abb30255bbe080c568d833df6b96a9e
diff --git a/meta-ampere/meta-mitchell/conf/templates/default/bblayers.conf.sample b/meta-ampere/meta-mitchell/conf/templates/default/bblayers.conf.sample
index a6e860f..7fa475c 100644
--- a/meta-ampere/meta-mitchell/conf/templates/default/bblayers.conf.sample
+++ b/meta-ampere/meta-mitchell/conf/templates/default/bblayers.conf.sample
@@ -17,15 +17,3 @@
   ##OEROOT##/meta-ampere \
   ##OEROOT##/meta-ampere/meta-mitchell \
   "
-BBLAYERS_NON_REMOVABLE ?= " \
-  ##OEROOT##/meta \
-  ##OEROOT##/meta-openembedded/meta-oe \
-  ##OEROOT##/meta-openembedded/meta-networking \
-  ##OEROOT##/meta-openembedded/meta-perl \
-  ##OEROOT##/meta-openembedded/meta-python \
-  ##OEROOT##/meta-security \
-  ##OEROOT##/meta-phosphor \
-  ##OEROOT##/meta-aspeed \
-  ##OEROOT##/meta-ampere \
-  ##OEROOT##/meta-ampere/meta-mitchell \
-  "