[renovate] Add launchdarkly github action (elastic#190535)

Adds the GitHub action `launchdarkly/find-code-references` to the
LaunchDarkly group of dependencies.

A pull request will be opened shortly after introducing sha pinning to
the dependency.

renovate.json

@@ -68,7 +68,7 @@
     },
     {
       "groupName": "LaunchDarkly",
-      "matchDepNames": ["launchdarkly-js-client-sdk", "@launchdarkly/node-server-sdk"],
+      "matchDepNames": ["launchdarkly-js-client-sdk", "@launchdarkly/node-server-sdk", "launchdarkly/find-code-references"],
       "reviewers": ["team:kibana-security", "team:kibana-core"],
       "matchBaseBranches": ["main"],
       "labels": ["release_note:skip", "Team:Security", "Team:Core", "backport:prev-minor"],