conf/layer.conf: Remove support to versions before dunfell

Remove the versions before dunfell as the new overrides
synthax is not supported by old releases.

Signed-off-by: Vinicius Aquino <[email protected]>

Author: Ossanes

conf/layer.conf

@@ -11,11 +11,6 @@ BBFILE_PRIORITY_rust-bin-layer = "7"
 LICENSE_PATH += "${LAYERDIR}/files/common-licenses"
 
 LAYERSERIES_COMPAT_rust-bin-layer = " \
-    sumo \
-    rocko \
-    thud \
-    warrior \
-    zeus \
     dunfell \
     gatesgarth \
     hardknott \