add cost monitor type to API Spec (#1996)

Co-authored-by: ci.datadog-api-spec <[email protected]>

Author: api-clients-generation-pipeline[bot]

.apigentools-info

@@ -4,13 +4,13 @@
     "spec_versions": {
         "v1": {
             "apigentools_version": "1.6.6",
-            "regenerated": "2025-01-14 15:59:07.108645",
-            "spec_repo_commit": "0457044b"
+            "regenerated": "2025-01-15 09:47:01.880563",
+            "spec_repo_commit": "21b02fc5"
         },
         "v2": {
             "apigentools_version": "1.6.6",
-            "regenerated": "2025-01-14 15:59:07.123971",
-            "spec_repo_commit": "0457044b"
+            "regenerated": "2025-01-15 09:47:01.895832",
+            "spec_repo_commit": "21b02fc5"
         }
     }
 }