[gn] Update link to v8 blog

In the description of the `v8_use_snapshot` gn arg, we had a link to
the old location of our blog.

R=mathias@chromium.org

No-Try: true
Change-Id: Ib7d0ae21f3e109b4fae9ca51a1c69d07d42f9017
Reviewed-on: https://chromium-review.googlesource.com/c/1392191Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58493}

gni/v8.gni

@@ -32,7 +32,7 @@ declare_args() {
   v8_enable_backtrace = ""
 
   # Enable the snapshot feature, for fast context creation.
-  # http://v8project.blogspot.com/2015/09/custom-startup-snapshots.html
+  # https://v8.dev/blog/custom-startup-snapshots
   # TODO(thakis): Make snapshots work in 64-bit win/cross builds,
   # https://803591
   v8_use_snapshot = !(is_win && host_os != "win" && target_cpu == "x64")