Update V8 version to 7.3

TBR=machenbach@chromium.org

Change-Id: Id131f9624b6cd8e72f45e0506644d9e9765fa6f2
Reviewed-on: https://chromium-review.googlesource.com/c/1354888Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Michael Hablich <hablich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57937}

include/v8-version.h

@@ -9,7 +9,7 @@
 // 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 7
-#define V8_MINOR_VERSION 2
+#define V8_MINOR_VERSION 3
 #define V8_BUILD_NUMBER 0
 #define V8_PATCH_LEVEL 0