[CI:DOCS] Disable Dependabot in favor of Renovate

Fixes: #18139

Removing the Dependabot configuration file is a required prerequisite to
stopping it from opening update PRs.  Once this commit is merged, the
`Dependabot security updates` repo. setting may also be disabled.  Note:
The `Dependabot alerts` setting should remain enabled, this provides
security-data to renovate for opening important vulnerability fix PRs.

Signed-off-by: Chris Evich <cevich@redhat.com>

.github/dependabot.yml

@@ -1,25 +0,0 @@
-version: 2
-updates:
-- package-ecosystem: gomod
-  directory: "/"
-  schedule:
-    interval: daily
-  labels:
-    - "release-note-none"
-  open-pull-requests-limit: 10
-
-- package-ecosystem: gomod
-  directory: "test/tools"
-  schedule:
-    interval: daily
-  labels:
-    - "release-note-none"
-  open-pull-requests-limit: 10
-
-- package-ecosystem: "github-actions"
-  directory: "/"
-  schedule:
-      interval: "daily"
-  labels:
-    - "release-note-none"
-  open-pull-requests-limit: 10