Make InvalidTransitionException a subclass of Exception

So far, this exception was subclassing IOException but this is more of a
logical exception than an I/O one.

Change-Id: Ic06b8877aa18bdb6e8830ae04d3454ab224e6cf6
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/base/its/InvalidTransitionException.java b/src/main/java/com/googlesource/gerrit/plugins/its/base/its/InvalidTransitionException.java
index 78c6ec5..949031b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/base/its/InvalidTransitionException.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/base/its/InvalidTransitionException.java
@@ -14,9 +14,7 @@
 
 package com.googlesource.gerrit.plugins.its.base.its;
 
-import java.io.IOException;
-
-public class InvalidTransitionException extends IOException {
+public class InvalidTransitionException extends Exception {
 
   private static final long serialVersionUID = 1L;