Anonymous authentication no longer works

[v-zhuravlev]

Hi, One thing I noticed, that if I'm not mistaken this PR makes authentication mandatory (which was optional in fact before that):
https://github.com/grafana/grizzly/pull/197/files#diff-6f38156d91a983d8aa26b50d3fb6dfb5764ea755a9cd5b7da70258e9be77cf92L31

so grr no longer works because token is always required, even if
anonymous access (which is quite useful for local dev environments, for example) is enabled.

# only GRAFANA_URL set in env:
wabbit@vzhuravl-mac node-mixin % env | grep GRAF
GRAFANA_URL=http://grafana.k3d.localhost:9999

# latest build:
wabbit@vzhuravl-mac node-mixin % ../../../grizzly/cmd/grr/grr  watch .  mixin.libsonnet
INFO[0000] Watching for changes                         
INFO[0001] Changes detected. Applyingmixin.libsonnet    
INFO[0001] Applying 6 resources                         
ERRO[0001] Error: Require GRAFANA_TOKEN                 

# version v0.2.0-beta2:
wabbit@vzhuravl-mac node-mixin % grr  watch .  mixin.libsonnet                         
2022-04-16 22:42:26.995077 I | 22:42:26 Watching for changes
2022-04-16 22:42:27.560048 I | 22:42:27 Changes detected. Applying mixin.libsonnet
Dashboard.nodes updated
Dashboard.node-multicluster-rsrc-use updated
Dashboard.node-rsrc-use updated
Dashboard.nodes-darwin updated

@PatMis16

[v-zhuravlev]

Fixed in #210