Update to use assert syntax

Author: lpil

gleam.toml

@@ -1,6 +1,6 @@
 name = "gleam_stdlib"
 version = "0.60.0"
-gleam = ">= 1.9.0"
+gleam = ">= 1.11.0"
 licences = ["Apache-2.0"]
 description = "A standard library for the Gleam programming language"