ci(dependabot): restore cargo PR limit so security + version PRs flow (#3)

Aligns with hyperpolymath/rsr-template-repo#37: open-pull-requests-limit: 0
empirically suppressed Dependabot SECURITY PRs in addition to version
updates. Restoring limit: 10 with grouped minor/patch updates to keep
noise contained while letting security advisories flow.

Author: hyperpolymath

.github/dependabot.yml

@@ -30,7 +30,14 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
-    open-pull-requests-limit: 0
+    open-pull-requests-limit: 10
+    groups:
+      cargo:
+        patterns:
+          - "*"
+        update-types:
+          - "minor"
+          - "patch"
 
   # Elixir/Mix
   - package-ecosystem: "mix"
@@ -54,4 +61,4 @@ updates:
   - package-ecosystem: "nix"
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: "weekly"