chrome/browser: add missing input for expired_flags_list_gen

This is to fix
https://ci.chromium.org/p/chromium/builders/ci/Deterministic%20Linux/25327

The script reads //chrome/VERSION
https://cs.chromium.org/chromium/src/tools/flags/generate_expired_list.py?l=31&rcl=1fbbcc1d5355dae3c52ed9a8c74f71bc4f4e7070

Change-Id: I0f1bd5e6e091e1cc3e016588f21ba8128f6d366d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1868218
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@google.com>
Cr-Commit-Position: refs/heads/master@{#707277}

chrome/browser/BUILD.gn

@@ -5389,6 +5389,9 @@ action("expired_flags_list_gen") {
   sources = [
     "flag-metadata.json",
   ]
+  inputs = [
+    "//chrome/VERSION",
+  ]
   outputs = [
     "$root_gen_dir/chrome/browser/expired_flags_list.cc",
   ]