Skip eager SDL validation on the unresolvable-type wrapper example

With `VALIDATE_GRAPHQL_SCHEMAS=1` (as on CI), the eager SDL validation
raised the unresolvable-type error during GraphQL schema generation,
before JSON schema generation could exercise the wrapped
`FieldReference#resolve` nil return the example exists to cover, leaving
that branch uncovered. Tagging the example with
`:dont_validate_graphql_schema` (the existing opt-out for intentionally
invalid schemas) makes the error surface via the JSON schema path in all
environments.

Author: jwils

elasticgraph-json_ingestion/spec/unit/elastic_graph/json_ingestion/schema_definition/indexing/wrappers_spec.rb

@@ -45,7 +45,11 @@ module JSONIngestion::SchemaDefinition
           })
         end
 
-        it "raises a clear error (rather than blowing up internally) for a field whose type never resolves" do
+        # `:dont_validate_graphql_schema` matters here: with `VALIDATE_GRAPHQL_SCHEMAS=1` (as on CI), the
+        # eager SDL validation would raise this error during GraphQL schema generation, before the JSON
+        # schema generation path exercises the wrapped `FieldReference#resolve` nil return that this
+        # example exists to cover.
+        it "raises a clear error (rather than blowing up internally) for a field whose type never resolves", :dont_validate_graphql_schema do
           # When a field references a type that is never defined, the wrapped `FieldReference#resolve`
           # returns `nil`. The schema definition machinery relies on that `nil` to detect the unresolvable
           # type and surface a helpful error instead of crashing.