Update Substrate version to 0.0.68

Author: gluon-bot

pom.xml

@@ -47,7 +47,7 @@
     <javadoc.plugin.version>3.5.0</javadoc.plugin.version>
     <gpg.plugin.version>3.1.0</gpg.plugin.version>
     <maven.plugin.version>3.9.9</maven.plugin.version>
-    <substrate.version>0.0.68-SNAPSHOT</substrate.version>
+    <substrate.version>0.0.68</substrate.version>
   </properties>
 
   <dependencies>