ax(mining): replace prose comment on wsUpgrader with usage example

AX Principle 2 — comments must show HOW (concrete call), not describe WHAT.
The wsUpgrader var comment restated the variable's purpose in prose; replaced
with a usage example showing the Upgrade call site.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/service.go

@@ -373,7 +373,7 @@ func requestTimeoutMiddleware(timeout time.Duration) gin.HandlerFunc {
 	}
 }
 
-// WebSocket upgrader for the events endpoint
+// conn, err := wsUpgrader.Upgrade(c.Writer, c.Request, nil) // upgrade HTTP to WebSocket
 var wsUpgrader = websocket.Upgrader{
 	ReadBufferSize:  1024,
 	WriteBufferSize: 1024,