Remove "Stage" variable

as we will use distinct Influx and Grafana instances for the different stages/environments.

deploy/grafana-dashboard/panels/poseidon.dashboard.py

@@ -3,16 +3,13 @@ from grafanalib.core import Dashboard, Templating, Time
 from panels.availability_row import availability_panels
 from panels.general_row import general_panels
 from panels.runner_insights_row import runner_insights_panels
-from utils.variables import stage_variable, environment_variable
+from utils.variables import environment_variable
 
 dashboard = Dashboard(
     title="Poseidon autogen",
     timezone="browser",
     panels=availability_panels + general_panels + runner_insights_panels,
-    templating=Templating(list=[
-        stage_variable,
-        environment_variable,
-    ]),
+    templating=Templating(list=[ environment_variable ]),
     editable=True,
     refresh="30s",
     time=Time("now-6h", "now"),