Currently the docker-compose examples for loading `victoriametrics-datasource` uses 2 environment variables:
- `GF_ALLOW_LOADING_UNSIGNED_PLUGINS`
- `GF_DEFAULT_APP_MODE`
I believe both of the env vars are trying to achieve the same thing. `GF_DEFAULT_APP_MODE` disables code signing for all plugins and `GF_ALLOW_LOADING_UNSIGNED_PLUGINS` intends to disable code signing for just `victoriametrics-datasource`.
Keeping the scope narrowed to just `victoriametrics-datasource` would be preferable in this case.
Unfortunately `GF_ALLOW_LOADING_UNSIGNED_PLUGINS` is misspelled. According to [grafana docs](https://grafana.com/docs/grafana/latest/setup-grafana/configure-grafana/#override-configuration-with-environment-variables), the format is supposed to be `GF_<SectionName>_<KeyName>`. In other words the current env var is missing the section name.
This PR proposes to:
1. fix the typo
2. remove the global disablement of code signing
Alternatively, if you prefer to keep codesigning disabled globally, please remove `GF_ALLOW_LOADING_UNSIGNED_PLUGINS` env var as it confuses things
