chore: resolve smithy build warnings (#5909)

Author: hpmellema

codegen/generic-client-test-codegen/model/weather.smithy

@@ -36,50 +36,61 @@ service Weather {
     ]
 }
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpApiKeyAuth")
 @auth([httpApiKeyAuth])
 operation OnlyHttpApiKeyAuth {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpBearerAuth")
 @auth([httpBearerAuth])
 operation OnlyHttpBearerAuth {}
 
+@readonly
 @http(method: "GET", uri: "/OnlySigv4Auth")
 @auth([sigv4])
 operation OnlySigv4Auth {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpApiKeyAndBearerAuth")
 @auth([httpApiKeyAuth, httpBearerAuth])
 operation OnlyHttpApiKeyAndBearerAuth {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpApiKeyAndBearerAuthReversed")
 @auth([httpBearerAuth, httpApiKeyAuth])
 operation OnlyHttpApiKeyAndBearerAuthReversed {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpApiKeyAuthOptional")
 @auth([httpApiKeyAuth])
 @optionalAuth
 operation OnlyHttpApiKeyAuthOptional {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyHttpBearerAuthOptional")
 @auth([httpBearerAuth])
 @optionalAuth
 operation OnlyHttpBearerAuthOptional {}
 
+@readonly
 @http(method: "GET", uri: "/OnlySigv4AuthOptional")
 @auth([sigv4])
 @optionalAuth
 operation OnlySigv4AuthOptional {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyCustomAuth")
 @auth([customAuth])
 operation OnlyCustomAuth {}
 
+@readonly
 @http(method: "GET", uri: "/OnlyCustomAuthOptional")
 @auth([customAuth])
 @optionalAuth
 operation OnlyCustomAuthOptional {}
 
+@readonly
 @http(method: "GET", uri: "/SameAsService")
 operation SameAsService {
   output := {