890 vz_google_sheets DAG: stop loading older years

[gabrielwol]

What this pull request accomplishes:

• Update vz_google_sheets DAG: replace the get_list_of_years task with one that reads from the airflow spreadsheets variable and also filters specific years. By default filters current and last year, but can be overridden by DAG param when triggered.
• Tested here with manual trigger and here with default (there is no 2024 sheet yet, so only 2023 was pulled)

Issue(s) this solves:

• #890

What, in particular, needs to reviewed:

What needs to be done by a sysadmin after this PR is merged

• update DAG symlink