fix: Remove assertion on HttpApiKey scheme being present in client co…

.changelog/1758067735.md

@@ -0,0 +1,9 @@
+---
+applies_to: ["client"]
+authors: ["haydenbaker"]
+references: ["smithy-rs#4226"]
+breaking: false
+new_feature: false
+bug_fix: true
+---
+Fixed problematic assertion on HttpApiKeyAuthTrait `scheme`, which was causing client-codegen to fail when the correct settings for api-key based auth were set.

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/customizations/HttpAuthDecorator.kt

@@ -180,13 +180,7 @@ private class HttpAuthServiceRuntimePluginCustomization(
                         val trait = serviceShape.getTrait<HttpApiKeyAuthTrait>()!!
                         val location =
                             when (trait.`in`!!) {
-                                HttpApiKeyAuthTrait.Location.HEADER -> {
-                                    check(trait.scheme.isPresent) {
-                                        "A scheme is required for `@httpApiKey` when `in` is set to `header`"
-                                    }
-                                    "Header"
-                                }
-
+                                HttpApiKeyAuthTrait.Location.HEADER -> "Header"
                                 HttpApiKeyAuthTrait.Location.QUERY -> "Query"
                             }