cleanup: Remove redundant config

...because it's already being set earlier in that config.

Change-Id: I413bc2d1cb43406d20e4a6bbbfec759abd8b5312
diff --git a/configs/czechlight_i686_container_defconfig b/configs/czechlight_i686_container_defconfig
index 48b21d3..27ed213 100644
--- a/configs/czechlight_i686_container_defconfig
+++ b/configs/czechlight_i686_container_defconfig
@@ -38,4 +38,3 @@
 # BR2_PACKAGE_VIM_RUNTIME is not set
 BR2_TARGET_ROOTFS_TAR_XZ=y
 CZECHLIGHT_NETCONF=y
-BR2_ROOTFS_OVERLAY="$(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/i686_container/overlay/"