Changed version number to 9.0

TBR=vahl@chromium.org

Change-Id: I4a1ebf06681f7618392b8d4915396e6edaf5dc10
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2629277Reviewed-by: Lutz Vahl <vahl@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Lutz Vahl <vahl@chromium.org>
Auto-Submit: Lutz Vahl <vahl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72091}

include/v8-version.h

@@ -8,8 +8,8 @@
 // These macros define the version number for the current version.
 // NOTE these macros are used by some of the tool scripts and the build
 // system so their names cannot be changed without changing the scripts.
-#define V8_MAJOR_VERSION 8
-#define V8_MINOR_VERSION 9
+#define V8_MAJOR_VERSION 9
+#define V8_MINOR_VERSION 0
 #define V8_BUILD_NUMBER 0
 #define V8_PATCH_LEVEL 0