fix: fix aqua g -i

[suzuki-shunsuke]

⚠️ Known Issue

When packages: is empty, aqua g -i ignores the ident of registries.

aqua.yaml

---
# aqua - Declarative CLI Version Manager
# https://aquaproj.github.io/
registries:
  - type: standard
    ref: v1.4.0 # renovate: depName=aquaproj/aqua-registry

packages:

$ aqua g -i cli/cli

Expected Result

---
# aqua - Declarative CLI Version Manager
# https://aquaproj.github.io/
registries:
  - type: standard
    ref: v1.4.0 # renovate: depName=aquaproj/aqua-registry
packages:
  - name: cli/cli@v2.5.1

Actual Result

---
# aqua - Declarative CLI Version Manager
# https://aquaproj.github.io/
registries:
  - type: standard
    ref: v1.4.0 # renovate: depName=aquaproj/aqua-registry
packages:
- name: cli/cli@v2.5.1