Decouple dryRun from SessionMetadata

dryRun is only available via the (sessionless!) tool, and is not
a property of the session.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125203026

java/google/registry/flows/SessionMetadata.java

@@ -137,12 +137,6 @@ public abstract class SessionMetadata {
     setPropertyChecked(FAILED_LOGIN_ATTEMPTS_KEY, null);
   }
 
-  // These three methods are here to allow special permissions if a derived class overrides them.
-
-  public boolean isDryRun() {
-    return false;
-  }
-
   @Override
   public String toString() {
     return toStringHelper(getClass())