chore(ci): two pre-existing tflint findings block a clean pre-commit run

[openbao-service-broker]

pre-commit run --all-files reports two tflint findings that predate any
current work and are unrelated to the files being changed:

1. .tflint.hcl:19:3 — Unsupported argument. An argument named "signature" is not expected here. The plugin schema no longer accepts that argument.
2. modules/repo-settings/variables.tf:49 — variable "gitflow" is declared
   but unused (terraform_unused_declarations). The module takes the flag but
   does not consume it; the git-flow wiring lives in the root module instead.

Both should be fixed rather than suppressed — either the argument is dropped
and the plugin config updated, or the module variable is removed and its
callers adjusted.

Surfaced while registering a repo; deliberately left untouched there to keep
that change scoped.