Update otelcol test package (#2971)

Update otelcol test package following current recommendations:
- Dataset in OTel packages should default to the related community receivers.
- "subobjects: false" at the root level conflicts with built-in templates .
- No fields are needed.

Author: jsoriano

test/packages/parallel/httpcheck/_dev/test/policy/test-eprcheck.expected

@@ -25,7 +25,7 @@ processors:
             - context: datapoint
               statements:
                 - set(attributes["data_stream.type"], "metrics")
-                - set(attributes["data_stream.dataset"], "httpcheck.check")
+                - set(attributes["data_stream.dataset"], "httpcheck.httpcheckreceiver")
                 - set(attributes["data_stream.namespace"], "ep")
 receivers:
     httpcheck/componentid-0:

test/packages/parallel/httpcheck/fields/base-fields.yml

@@ -26,7 +26,7 @@ icons:
     size: 32x32
     type: image/svg+xml
 policy_templates:
-  - name: check
+  - name: httpcheckreceiver
     type: metrics
     title: HTTP Check
     description: Perform HTTP checks and collect its results.
@@ -67,10 +67,6 @@ policy_templates:
         multi: true
         required: false
         show_user: false
-elasticsearch:
-  index_template:
-    mappings:
-      subobjects: false
 owner:
   github: elastic/ecosystem
   type: elastic