chore(deps): remove dependabot version updates (#122)

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

.github/dependabot.yml

@@ -1,29 +0,0 @@
-version: 2
-updates:
-  - package-ecosystem: "npm"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    commit-message:
-      prefix: "chore(deps)"
-    groups:
-      minor-and-patch:
-        update-types:
-          - "minor"
-          - "patch"
-    ignore:
-      # @types/node must track the runtime Node major, not the latest release.
-      # This is a pure CDK app (no Lambdas); it is built/synthed on Node 24, so
-      # @types/node is pinned to ^24. Dependabot can't see the build Node and a
-      # too-new types major still compiles, so a major bump passes CI while being
-      # wrong. This is the sanctioned exception to the no-blanket-ignore rule
-      # (engineering-handbook github-standards Pinning Principle). Bump deliberately
-      # alongside a Node upgrade. Minor/patch within the current major still flow.
-      - dependency-name: "@types/node"
-        update-types: ["version-update:semver-major"]
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    commit-message:
-      prefix: "chore(deps)"