ngalert openapi: Fix ObjectMatchers definition (#79477)

These don't get marshalled and unmarshalled in the same way as they are represented in Go
This PR changes the OpenAPI spec to reflect what the API accepts and sends back

pkg/services/ngalert/api/tooling/api.json

@@ -2270,9 +2270,18 @@
    "title": "OAuth2 is the oauth2 client configuration.",
    "type": "object"
   },
+  "ObjectMatcher": {
+   "items": {
+    "type": "string"
+   },
+   "title": "ObjectMatcher is a matcher that can be used to filter alerts.",
+   "type": "array"
+  },
   "ObjectMatchers": {
-   "$ref": "#/definitions/Matchers",
-   "description": "ObjectMatchers is Matchers with a different Unmarshal and Marshal methods that accept matchers as objects\nthat have already been parsed."
+   "items": {
+    "$ref": "#/definitions/ObjectMatcher"
+   },
+   "type": "array"
   },
   "OpsGenieConfig": {
    "properties": {
@@ -4414,6 +4423,7 @@
    "type": "object"
   },
   "alertGroup": {
+   "description": "AlertGroup alert group",
    "properties": {
     "alerts": {
      "description": "alerts",
@@ -4542,7 +4552,6 @@
    "type": "object"
   },
   "gettableAlert": {
-   "description": "GettableAlert gettable alert",
    "properties": {
     "annotations": {
      "$ref": "#/definitions/labelSet"
@@ -4652,13 +4661,13 @@
    "type": "object"
   },
   "gettableSilences": {
+   "description": "GettableSilences gettable silences",
    "items": {
     "$ref": "#/definitions/gettableSilence"
    },
    "type": "array"
   },
   "integration": {
-   "description": "Integration integration",
    "properties": {
     "lastNotifyAttempt": {
      "description": "A timestamp indicating the last attempt to deliver a notification regardless of the outcome.\nFormat: date-time",