ci: only publish docs in master and tagged releases

Until now, docs have been published for every master and
release branch build. This can lead to confusion if a new
feature is backported to the release branch and the docs
are published to the website, even though the feature will
not be available until the next tagged release.

This does have the effect that small doc-only fixes will
not be in the latest release docs until we actually tag
a release.

Signed-off-by: Travis Nielsen <tnielsen@redhat.com>
(cherry picked from commit 28fa387dff)

build/release/Makefile

@@ -51,7 +51,14 @@ PLATFORMS ?= $(ALL_PLATFORMS)
 
 # "helm" flavor is for pushing to s3/https endpoint
 # "charts" flavor is for pushing to oci endpoint
-FLAVORS ?= output images docs helm charts
+FLAVORS ?= output images helm charts
+
+# Only publish the docs if in master branch or if this is a tagged release.
+ifeq ($(shell echo $(BRANCH_NAME)),master)
+FLAVORS += docs
+else ifeq ($(TAGGED_RELEASE),true)
+FLAVORS += docs
+endif
 
 DOCKER_REGISTRY ?= docker.io/rook
 QUAY_REGISTRY ?= quay.io/rook