Run Dependabot more frequently

  - Ignore patch updates
  - Lift open PR limit
  - Reformat `dependabot.yml`

.github/dependabot.yml

@@ -1,14 +1,17 @@
 version: 2
 updates:
-- package-ecosystem: cargo
-  directory: "/"
-  schedule:
-    interval: monthly
-    time: "02:00"
-  open-pull-requests-limit: 2
-- package-ecosystem: github-actions
-  directory: "/"
-  schedule:
-    interval: monthly
-    time: "02:00"
-  open-pull-requests-limit: 2
+  - package-ecosystem: cargo
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+    ignore:
+      # `dependency-name` is required.
+      - dependency-name: "*"
+        update-types: ["version-update:semver-patch"]
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday