MergeChangeCommand: Remove unreachable 'throw new IOException()'

The isMergedInto method returns a boolean, which can never
be null.

Change-Id: Ie8271bb1a511f35e305196340b0bed1733fdb160

src/main/java/com/googlesource/gerrit/plugins/batch/ssh/MergeChangeCommand.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/batch/ssh/MergeChangeCommand.java b/src/main/java/com/googlesource/gerrit/plugins/batch/ssh/MergeChangeCommand.java
index 932b000..a18b35b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/batch/ssh/MergeChangeCommand.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/batch/ssh/MergeChangeCommand.java
@@ -137,11 +137,7 @@
     }
     for (ObjectId parent : parents) {
       Project.NameKey project = psarg.change.getDest().getParentKey();
-      Boolean isMergedInto = isMergedInto(project, parent, sha1);
-      if (isMergedInto == null) {
-        throw new IOException();
-      }
-      if (isMergedInto) {
+      if (isMergedInto(project, parent, sha1)) {
         return true;
       }
     }