[DOCS] Change `detector_rules` to `rules` in ML docs

Original commit: elastic/x-pack-elasticsearch@49699286d3

docs/en/rest-api/ml/get-job.asciidoc

@@ -81,7 +81,7 @@ The API returns the following results:
             "function": "mean",
             "field_name": "responsetime",
             "partition_field_name": "airline",
-            "detector_rules": [],
+            "rules": [],
             "detector_index": 0
           }
         ],

docs/en/rest-api/ml/jobresource.asciidoc

@@ -249,7 +249,7 @@ is different from one named 'bytes'.
 
 ////
 LEAVE UNDOCUMENTED
- `detector_rules`::
+ `rules`::
   (array) TBD
 ////
 

docs/en/rest-api/ml/put-job.asciidoc

@@ -121,7 +121,7 @@ When the job is created, you receive the following results:
         "detector_description": "low_sum(events_per_min)",
         "function": "low_sum",
         "field_name": "events_per_min",
-        "detector_rules": [],
+        "rules": [],
         "detector_index": 0
       }
     ],

docs/en/rest-api/ml/update-job.asciidoc

@@ -136,7 +136,7 @@ information, including the updated property values. For example:
         "detector_description": "Unusual message counts",
         "function": "count",
         "by_field_name": "mlcategory",
-        "detector_rules": [],
+        "rules": [],
         "detector_index": 0
       }
     ],