build(platforms): drop linux/s390x & linux/ppc64le

Author: isometry

Makefile

@@ -176,7 +176,7 @@ docker-push: ## Push docker image with the manager.
 # - have enabled BuildKit. More info: https://docs.docker.com/develop/develop-images/build_enhancements/
 # - be able to push the image to your registry (i.e. if you do not set a valid value via IMG=<myregistry/image:<tag>> then the export will fail)
 # To adequately provide solutions that are compatible with multiple platforms, you should consider using this option.
-PLATFORMS ?= linux/arm64,linux/amd64,linux/s390x,linux/ppc64le
+PLATFORMS ?= linux/arm64,linux/amd64
 .PHONY: docker-buildx
 docker-buildx: ## Build and push docker image for the manager for cross-platform support
 	# copy existing Dockerfile and insert --platform=${BUILDPLATFORM} into Dockerfile.cross, and preserve the original Dockerfile