Update version for v4.0.0-rc3 release

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/VERSION b/VERSION
index 5b9105c..859ede9 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.1.92
+3.1.93