Address review comments

Address review comments from similar PR gardener/gardener-extension-networking-calico#327.

.ci/verify

@@ -9,9 +9,4 @@ cd "$(dirname $0)/.."
 git config --global user.email "gardener@sap.com"
 git config --global user.name "Gardener CI/CD"
 
-# Required due to https://github.com/kubernetes/kubernetes/issues/86753 - can be removed once the issue is fixed.
-mkdir -p /go/src/github.com/gardener/gardener-extension-provider-gcp
-cp -r . /go/src/github.com/gardener/gardener-extension-provider-gcp
-cd /go/src/github.com/gardener/gardener-extension-provider-gcp
-
 make verify-extended

Makefile

@@ -57,7 +57,7 @@ include $(GARDENER_HACK_DIR)/tools.mk
 
 .PHONY: start
 start:
-	@LEADER_ELECTION_NAMESPACE=garden GO111MODULE=on go run \
+	@LEADER_ELECTION_NAMESPACE=garden go run \
 		-ldflags $(LD_FLAGS) \
 		./cmd/$(EXTENSION_PREFIX)-$(NAME) \
 		--config-file=./example/00-componentconfig.yaml \
@@ -71,7 +71,7 @@ start:
 
 .PHONY: start-admission
 start-admission:
-	@LEADER_ELECTION_NAMESPACE=garden GO111MODULE=on go run \
+	@LEADER_ELECTION_NAMESPACE=garden go run \
 		-ldflags $(LD_FLAGS) \
 		./cmd/$(EXTENSION_PREFIX)-$(ADMISSION_NAME) \
 		--webhook-config-server-host=0.0.0.0 \
@@ -103,7 +103,7 @@ docker-images:
 
 .PHONY: tidy
 tidy:
-	@GO111MODULE=on go mod tidy
+	@go mod tidy
 	@mkdir -p $(REPO_ROOT)/.ci/hack && cp $(GARDENER_HACK_DIR)/.ci/* $(REPO_ROOT)/.ci/hack/ && chmod +xw $(REPO_ROOT)/.ci/hack/*
 	@GARDENER_HACK_DIR=$(GARDENER_HACK_DIR) bash $(REPO_ROOT)/hack/update-github-templates.sh
 	@cp $(GARDENER_HACK_DIR)/cherry-pick-pull.sh $(HACK_DIR)/cherry-pick-pull.sh && chmod +xw $(HACK_DIR)/cherry-pick-pull.sh

hack/update-codegen.sh

@@ -29,8 +29,6 @@ export GO111MODULE=off
 
 rm -f $GOPATH/bin/*-gen
 
-PROJECT_ROOT=$(dirname $0)/..
-
 bash "${CODE_GEN_DIR}/generate-internal-groups.sh" \
   deepcopy,defaulter \
   github.com/gardener/gardener-extension-provider-gcp/pkg/client \