ci(deps): ignore the regressed keyring 4.1.6 in dependabot (#319)

keyring 4.1.6 caches the first native-store construction failure forever
(LazyLock latch), which defeats the test suite's in-memory store
isolation and panics the_test_suite_is_isolated_from_the_os_keychain on
headless ubuntu CI. It was pinned back to 4.1.5 in #298; this stops
dependabot re-offering the same broken version every week. Drop the
ignore when an upstream fix ships.

README checked, no changes needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_019xKUm9vH4ifb5LHR5szy1v

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: pmaxhogan

.github/dependabot.yml

@@ -20,6 +20,14 @@ updates:
     commit-message:
       prefix: "build(deps)"
       prefix-development: "build(deps-dev)"
+    ignore:
+      # keyring 4.1.6 regressed: it caches the first native-store failure
+      # forever, defeating the in-memory test-store latch and panicking
+      # the_test_suite_is_isolated_from_the_os_keychain on headless CI
+      # (no Secret Service). Pinned back in #298; drop this ignore once a
+      # release fixes the LazyLock latch upstream.
+      - dependency-name: keyring
+        versions: ["4.1.6"]
     groups:
       cargo-minor-patch:
         update-types: