🌱 Makefile: re-enable hack/tools on make help

[chrischdi]

What this PR does / why we need it:

• Fixes regression for make help introduced in 🌱 Install hack/tools with temporary go module #5741

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):

fixes #6444

What else to add

Before:

$ make
...
  clean-release-git                              Restores the git files usually modified during a release
  clean-generated-conversions                    Remove files generated by conversion-gen from the mentioned dirs. Example SRC_DIRS="./api/v1alpha4"

hack/tools:

After:

$ make
...
  clean-release-git                              Restores the git files usually modified during a release
  clean-generated-conversions                    Remove files generated by conversion-gen from the mentioned dirs. Example SRC_DIRS="./api/v1alpha4"

hack/tools:
  controller-gen                                 Build a local copy of controller-gen.
  conversion-gen                                 Build a local copy of conversion-gen.
  conversion-verifier                            Build a local copy of conversion-verifier.
  gotestsum                                      Build a local copy of gotestsum.
  go-apidiff                                     Build a local copy of go-apidiff
  envsubst                                       Build a local copy of envsubst.
  kustomize                                      Build a local copy of kustomize.
  setup-envtest                                  Build a local copy of setup-envtest.
  kpromo                                         Build a local copy of kpromo
  tilt-prepare                                   Build a local copy of tilt-prepare.
  golangci-lint                                  Build a local copy of golangci-lint

[sbueringer]

Thank you!

Verified and works

/lgtm
/approve

[k8s-ci-robot]

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This pull-request has been approved by: sbueringer

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