chore: upgrade smithy-kotlin version (#699)

Author: ianbotsf

gradle.properties

@@ -12,7 +12,7 @@ sdkVersion=0.17.6-SNAPSHOT
 smithyVersion=1.23.0
 smithyGradleVersion=0.6.0
 # smithy-kotlin codegen and runtime are versioned together
-smithyKotlinVersion=0.12.6-SNAPSHOT
+smithyKotlinVersion=0.12.6
 
 # kotlin
 kotlinVersion=1.7.10
@@ -39,4 +39,4 @@ slf4jVersion=1.7.36
 
 # dokka config (values specified at build-time as needed)
 smithyKotlinPackageListUrl=
-smithyKotlinDocBaseUrl=https://docs.aws.amazon.com/sdk-for-kotlin/latest/reference/smithy-kotlin
+smithyKotlinDocBaseUrl=https://docs.aws.amazon.com/sdk-for-kotlin/latest/reference/smithy-kotlin