chore: APM agent json server schema 20bb1f9ac324c275c41f6f81ac0e5ef93... (#4387)

Author: elastic-observability-automation[bot]

test/integration/api-schema/apm-server-schema/span.json

@@ -188,6 +188,9 @@
                 "object"
               ],
               "properties": {
+                "body": {
+                  "description": "The http request body usually as a string, but may be a dictionary for multipart/form-data content"
+                },
                 "id": {
                   "description": "ID holds the unique identifier for the http request.",
                   "type": [