chore: remove dependabot.yml — security-only via repo defaults (#254)

Conformance is a leaf CLI; scheduled version bumps are churn. Deleting
the config disables version-update PRs entirely. Security advisories
remain enabled via repo settings (Code security > Dependabot).

.github/dependabot.yml

@@ -1,42 +0,0 @@
-version: 2
-
-# Security updates always come through regardless of these settings.
-# Scheduled (non-security) updates are limited to minor/patch only —
-# major bumps of devDeps like eslint/typescript are manual decisions.
-
-updates:
-  - package-ecosystem: npm
-    directory: /
-    schedule:
-      interval: monthly
-    groups:
-      all-dependencies:
-        patterns:
-          - '*'
-    ignore:
-      - dependency-name: '*'
-        update-types: ['version-update:semver-major']
-
-  - package-ecosystem: npm
-    directory: /examples/servers/typescript
-    schedule:
-      interval: monthly
-    groups:
-      all-dependencies:
-        patterns:
-          - '*'
-    ignore:
-      - dependency-name: '*'
-        update-types: ['version-update:semver-major']
-
-  - package-ecosystem: github-actions
-    directory: /
-    schedule:
-      interval: monthly
-    groups:
-      all-actions:
-        patterns:
-          - '*'
-    ignore:
-      - dependency-name: '*'
-        update-types: ['version-update:semver-major']