build(deps): bump third_party/gflags from `03a4842` to `52e9456`

Bumps [third_party/gflags](https://github.com/gflags/gflags) from `03a4842` to `52e9456`.
- [Release notes](https://github.com/gflags/gflags/releases)
- [Commits](https://github.com/gflags/gflags/compare/03a4842c9c6aaef438d7bf0c84e8a62c8064992b...52e94563eba1968783864942fedf6e87e3c611f4)

---
updated-dependencies:
- dependency-name: third_party/gflags
  dependency-version: 52e94563eba1968783864942fedf6e87e3c611f4
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/third_party/gflags b/third_party/gflags
index 03a4842..52e9456 160000
--- a/third_party/gflags
+++ b/third_party/gflags
@@ -1 +1 @@
-Subproject commit 03a4842c9c6aaef438d7bf0c84e8a62c8064992b
+Subproject commit 52e94563eba1968783864942fedf6e87e3c611f4