Revert "makefile: run go mod vendor|tidy as first during make generate"

We needed to vendor during `make generate` to get `operator-sdk`
passing. We now just ran operator-sdk, so this temporary workaround is
no longer necessary and is reverted.

This reverts commit 67b44c3f99061d8c56eac095ac2b8890ad351c5d.

Author: thom311

Makefile

@@ -165,7 +165,7 @@ vendor:
 	done
 
 .PHONY: generate
-generate: vendor controller-gen ## Generate code containing DeepCopy, DeepCopyInto, and DeepCopyObject method implementations.
+generate: controller-gen ## Generate code containing DeepCopy, DeepCopyInto, and DeepCopyObject method implementations.
 	GOFLAGS='' $(CONTROLLER_GEN) object:headerFile="hack/boilerplate.go.txt" paths="./..."
 
 .PHONY: generate-check