Fix a linebreak (#86739) (#86742)

(cherry picked from commit 5ee3bbaa7939e164452d1c7946ac86b6737fef2c)

Co-authored-by: Ugo Sangiorgi <ugo.sangiorgi@elastic.co>

docs/reference/mapping/runtime.asciidoc

@@ -1184,8 +1184,7 @@ POST my-index-000001/_search
       }
     }
   },
-  "fields": [
-    "voltage_corrected", "node"]
+  "fields": ["voltage_corrected", "node"]
 }
 ----
 // TEST[continued]