docs(using-environment-variables): add mirror node chart upgrade retry variables (#295)

Signed-off-by: Fantomasa <ivailoinfo@gmail.com>

Author: Fantomasa

content/en/docs/advanced-solo-setup/using-environment-variables.md

@@ -158,6 +158,8 @@ Add-Content $PROFILE '$env:CONSENSUS_NODE_VERSION = "v0.73.0"'
 | `MIRROR_NODE_SCHEMA_READY_DELAY` | Interval between Mirror Node database schema checks, in milliseconds | `2000`
 | `MIRROR_NODE_IMPORTER_DETECT_MAX_ATTEMPTS` | Maximum number of attempts to detect a running Mirror Node importer pod. If no importer pod is found, the database schema wait is skipped | `15`
 | `MIRROR_NODE_IMPORTER_DETECT_DELAY` | Interval between Mirror Node importer pod detection attempts, in milliseconds | `2000`
+| `MIRROR_NODE_CHART_UPGRADE_MAX_ATTEMPTS` | Maximum number of attempts to install or upgrade the Mirror Node Helm chart before failing. Retries ride out transient Kubernetes API server outages | `3`
+| `MIRROR_NODE_CHART_UPGRADE_RETRY_DELAY_SECS` | Delay between Mirror Node Helm chart install/upgrade attempts, in seconds | `15`
 
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