fix: integration dashboard, [Elastic Agent] Errors counter shows files_opened_total (#14752)

Update `[Elastic Agent] Filestream Input Metrics` dashboard, Use `filebeat_input.processing_errors_total` for the `[Elastic Agent] Errors` counter.

Author: biscout42

packages/elastic_agent/kibana/dashboard/elastic_agent-ea44c820-95cb-11ee-b517-0550321b54cc.json

@@ -921,7 +921,7 @@
                                                     "dataType": "number",
                                                     "filter": {
                                                         "language": "kuery",
-                                                        "query": "\"filebeat_input.files_opened_total\": *"
+                                                        "query": "\"filebeat_input.processing_errors_total\": *"
                                                     },
                                                     "isBucketed": false,
                                                     "label": "Errors Total",
@@ -936,7 +936,7 @@
                                                         "sortField": "@timestamp"
                                                     },
                                                     "scale": "ratio",
-                                                    "sourceField": "filebeat_input.files_opened_total"
+                                                    "sourceField": "filebeat_input.processing_errors_total"
                                                 }
                                             },
                                             "incompleteColumns": {},