Convert override syntax to new version

For details see:
https://docs.yoctoproject.org/next/migration-guides/migration-3.4.html

Note that due to this change the latest point release of Dunfell is
the minimal requirement to be compatible with this layer.

recipes-integration/packagegroups/packagegroup-plasma-mobile-workspace.bb

@@ -14,7 +14,7 @@ inherit packagegroup features_check
 
 REQUIRED_DISTRO_FEATURES = "wayland x11 kde"
 
-RDEPENDS_${PN} = " \
+RDEPENDS:${PN} = " \
     bluedevil \
     breeze \
     discover \