chore: Tweak error message for $ref resolution failures

Author: edgarrmondragon

singer_sdk/schema/source.py

@@ -229,7 +229,7 @@ def fetch_schema(self, key: str) -> dict[str, t.Any]:
             resolved_schema = resolve_schema_references(schema)
             return resolved_schema.get("components", {}).get("schemas", {}).get(key, {})  # type: ignore[no-any-return]
         except PointerToNowhere as e:
-            msg = f"Schema component '{key}' not found"
+            msg = f"Failed to resolve schema references for '{key}'"
             raise SchemaNotFoundError(msg) from e