Update patch version for release - new version is 1.6.22-dev

Change-Id: I7741e6f3e2a8d45a4d154487f74c9edfdcb222dd
diff --git a/src/main/java/com/android/tools/r8/Version.java b/src/main/java/com/android/tools/r8/Version.java
index 418b038..5ff94ce 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 = "1.6.21-dev";
+  public static final String LABEL = "1.6.22-dev";
 
   private Version() {
   }