chore(deps): remove dependabot version updates (#45)

Renovate is the version-update bot. GitHub Dependabot alerts stay.

.github/dependabot.yml

@@ -1,28 +0,0 @@
-version: 2
-updates:
-  - package-ecosystem: "npm"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    groups:
-      minor-and-patch:
-        update-types:
-          - "minor"
-          - "patch"
-    ignore:
-      # @types/node must track the runtime Node major, not the latest release.
-      # Pure-CDK repo: the runtime is the Node that runs `cdk synth`/`tsc` in CI.
-      # Dependabot can't see that and a too-new types major still compiles (passes
-      # CI, wrong at runtime). Sanctioned exception to the no-blanket-ignore rule
-      # (engineering-handbook github-standards Pinning Principle). Minor/patch flow.
-      - dependency-name: "@types/node"
-        update-types: ["version-update:semver-major"]
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    groups:
-      minor-and-patch:
-        update-types:
-          - "minor"
-          - "patch"