fix: reject content-type header for empty body requests

Author: smilkuri

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpBindingProtocolGenerator.java

@@ -1868,7 +1868,7 @@ private void handleContentType(
             if (optionalContentType.isPresent() || operation.getInput().isPresent()) {
                 String contentType = optionalContentType.orElse(getDocumentContentType());
                 // If the operation accepts a content type, it must be either unset or the expected value.
-                writer.openBlock("if (contentType !== undefined && contentType !== $S) {", "};", contentType, () -> {
+                writer.openBlock("if (contentType !== undefined) {", "};", contentType, () -> {
                     writer.write("throw new __UnsupportedMediaTypeException();");
                 });
             } else {