layer.conf: Increase layer version to 6

This means we can use this as a test to enable certain autobuilder tests
such as testsdk.

(From OE-Core rev: dbfb2efcd7240a0a6a413f1b37c399b66fa79ca9)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/layer.conf

@@ -9,7 +9,7 @@ BBFILE_PRIORITY_core = "5"
 
 # This should only be incremented on significant changes that will
 # cause compatibility issues with other layers
-LAYERVERSION_core = "5"
+LAYERVERSION_core = "6"
 
 BBLAYERS_LAYERINDEX_NAME_core = "openembedded-core"