Stop generating fields.asciidoc

We won't be updating libbeat fields.yml anymore,
so no need to keep regenerating fields.asciidoc.

Makefile

@@ -122,7 +122,6 @@ fields_sources=\
 fields: include/fields.go x-pack/apm-server/include/fields.go
 include/fields.go x-pack/apm-server/include/fields.go: $(MAGE) magefile.go $(fields_sources)
 	@$(MAGE) fields
-	@mv docs/fields.asciidoc docs/legacy/fields.asciidoc
 
 config: apm-server.yml apm-server.docker.yml
 apm-server.yml apm-server.docker.yml: $(MAGE) magefile.go _meta/beat.yml

magefile.go

@@ -202,21 +202,17 @@ func Fields() error {
 	xpackFieldsModules := []string{mage.XPackBeatDir()}
 	allFieldsModules := append(ossFieldsModules[:], xpackFieldsModules...)
 
-	// Create include/fields.go from the OSS-only fields.
+	// Create include/fields.go and fields.yml from the OSS-only fields,
+	// and fields.all.yml from all fields.
 	if err := generateFieldsYAML(mage.FieldsYML, ossFieldsModules...); err != nil {
 		return err
 	}
 	if err := mage.GenerateFieldsGo(mage.FieldsYML, fieldsInclude); err != nil {
 		return err
 	}
-
-	// Create docs/fields.asciidoc from all fields from all license types.
 	if err := generateFieldsYAML(mage.FieldsAllYML, allFieldsModules...); err != nil {
 		return err
 	}
-	if err := mage.Docs.FieldDocs(mage.FieldsAllYML); err != nil {
-		return err
-	}
 
 	// Create x-pack/apm-server/include/fields.go from the X-Pack fields.
 	// These supplement the OSS fields, they don't replace them.