chore: prepare for 0.13.1-beta release

Author: ianbotsf

gradle.properties

@@ -6,7 +6,7 @@ kotlin.native.ignoreDisabledTargets=true
 org.gradle.jvmargs=-Xmx6g -XX:MaxPermSize=6g -XX:MaxMetaspaceSize=1G
 
 # sdk
-sdkVersion=0.13.0-beta
+sdkVersion=0.13.1-beta
 
 # codegen
 smithyVersion=1.17.0