[flutter_template_images] Minor cleanup (#1951)

Author: stuartmorgan-g

packages/flutter_template_images/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 4.1.1
+
+* Removes empty Dart file.
+* Opts in to NNBD (which is a no-op) so it's not flagged by pub.dev.
+
 ## 4.1.0
 
 * Updates package description.

packages/flutter_template_images/lib/flutter_template_images.dart

@@ -2,7 +2,7 @@ name: flutter_template_images
 description: Image files for use in flutter_tools templates without adding binary files to flutter/flutter.
 repository: https://github.com/flutter/packages/tree/main/packages/flutter_template_images
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+flutter_template_images%22
-version: 4.1.0
+version: 4.1.1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"