Update patch version for release - new version is 1.4.20-dev

Change-Id: Ic01ea1c228e66c9d153548711593e57442dc6b9e
diff --git a/src/main/java/com/android/tools/r8/Version.java b/src/main/java/com/android/tools/r8/Version.java
index 4288e55..908c4c5 100644
--- a/src/main/java/com/android/tools/r8/Version.java
+++ b/src/main/java/com/android/tools/r8/Version.java
@@ -11,7 +11,7 @@
 
   // This field is accessed from release scripts using simple pattern matching.
   // Therefore, changing this field could break our release scripts.
-  public static final String LABEL = "1.4.19-dev";
+  public static final String LABEL = "1.4.20-dev";
 
   private Version() {
   }