Update GitpodWorkspaceTooManyRegularNotActive severity level

Author: Prince Rachit Sinha

operations/observability/mixins/workspace/rules/components/workspaces/alerts.libsonnet

@@ -61,16 +61,16 @@
           {
             alert: 'GitpodWorkspaceTooManyRegularNotActive',
             labels: {
-              severity: 'warning',
+              severity: 'critical',
             },
-            'for': '10m',
+            'for': '15m',
             annotations: {
               runbook_url: 'none',
               summary: 'too many running but inactive workspaces',
               description: 'too many running but inactive workspaces',
             },
             expr: |||
-              gitpod_workspace_regular_not_active_percentage > 0.10 AND sum(gitpod_ws_manager_workspace_activity_total) > 100
+              gitpod_workspace_regular_not_active_percentage > 0.15 AND sum(gitpod_ws_manager_workspace_activity_total) > 100
             |||,
           },
         ],