Update version for v4.2.0-rc3 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 99988b0..2333c33 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.1.92
+4.1.93