remove redundant experiment

pkgs/source_maps/analysis_options.yaml

diff --git a/pkgs/source_maps/analysis_options.yaml b/pkgs/source_maps/analysis_options.yaml
index 86c8367..4f9dfb0 100644
--- a/pkgs/source_maps/analysis_options.yaml
+++ b/pkgs/source_maps/analysis_options.yaml
@@ -1,9 +1,5 @@
 include: package:pedantic/analysis_options.yaml
 
-analyzer:
-  enable-experiment:
-    - non-nullable
-
 linter:
   rules:
     - comment_references