Update patch version for release - new version is 1.6.13-dev

Change-Id: Ib83774e9b2ffe72dc0ec0435bf396720a4265183
diff --git a/src/main/java/com/android/tools/r8/Version.java b/src/main/java/com/android/tools/r8/Version.java
index 852c252..e43ef95 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 = "1.6.12-dev";
+  public static final String LABEL = "1.6.13-dev";
 
   private Version() {
   }