goreleaser: don't rely on ci-make-docs

Since the ci-make-docs target is no longer part of the Makefile, we
cannot rely on it for making the latest docs, and therefore we must
remove that from the goreleaser file too.

.goreleaser.yml

@@ -10,9 +10,6 @@ before:
     # We strongly recommend running tests to catch any regression before release.
     # Even though, this an optional step.
     - go test ./...
-    # As part of the release doc files are included as a separate deliverable for
-    # consumption by Packer.io. To include a separate docs.zip uncomment the following command.
-    - make ci-release-docs
     # Check plugin compatibility with required version of the Packer SDK
     - make plugin-check
 builds: