Depend on release version 2.12.0 of the SDK.
diff --git a/pubspec.yaml b/pubspec.yaml
index fcfbb91..9c5cb6b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,7 +5,7 @@
   Constants for ASCII and common non-ASCII character codes.
 
 environment:
-  sdk: ">=2.12.0-0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dev_dependencies:
   test: ^1.16.0-nullsafety