Increment CTS Version to 2.1_r4

Bug 2923901

Change-Id: I2e42eae1403eeee8e2386394a654f4a2276749a2
diff --git a/tools/host/src/com/android/cts/Version.java b/tools/host/src/com/android/cts/Version.java
index 4bdb3ed..257cf8a 100644
--- a/tools/host/src/com/android/cts/Version.java
+++ b/tools/host/src/com/android/cts/Version.java
@@ -18,12 +18,12 @@
 
 public class Version {
     // The CTS version string
-    private static final String version = "2.1_r3";
-    
+    private static final String version = "2.1_r4";
+
     private Version() {
         // no instances allowed
     }
-    
+
     public static String asString() {
         return version;
     }