Deprecate BOARD_BUILD_GKI_BOOT_IMAGE_WITHOUT_RAMDISK

These variables are no longer used. We don't build GKI in the platform
tree anymore. Remove these vars as we are not maintaining these.

Bug: 229701033
Test: presubmit
Change-Id: I7551aa37a049f3bc9252559a18feb0f6bdf0a548

bp2build/bp2build_product_config.go

@@ -793,9 +793,6 @@ func generateImagePropDictionary(variables *android.PartitionVariables, partitio
 	if variables.BoardUsesRecoveryAsBoot {
 		ret["recovery_as_boot"] = "true"
 	}
-	if variables.BoardBuildGkiBootImageWithoutRamdisk {
-		ret["gki_boot_image_without_ramdisk"] = "true"
-	}
 	if variables.ProductUseDynamicPartitionSize {
 		ret["use_dynamic_partition_size"] = "true"
 	}