build: Fix "make create-github-release"

Fix the `create-github-release` make target to use "go run" to run the
tool that creates the github release. This used to run a tool in this
repository that was pre-built, so the "go run" was not needed before.
Now the tool has moved to a separate repository, this is required.

Makefile

@@ -1826,7 +1826,7 @@ changelog:
 #
 # For more information on release notes generation see:
 #   https://github.com/gravitational/shared-workflows/tree/gus/release-notes/tools/release-notes#readme
-RELEASE_NOTES_GEN = github.com/gravitational/shared-workflows/tools/release-notes@latest
+RELEASE_NOTES_GEN = go run github.com/gravitational/shared-workflows/tools/release-notes@latest
 .PHONY: create-github-release
 create-github-release: LATEST = false
 create-github-release: GITHUB_RELEASE_LABELS = ""