build(deps): bump third_party/abseil-cpp from `fad9462` to `27478af` (#2284)

Bumps [third_party/abseil-cpp](https://github.com/abseil/abseil-cpp) from `fad9462` to `27478af`.
- [Release notes](https://github.com/abseil/abseil-cpp/releases)
- [Commits](https://github.com/abseil/abseil-cpp/compare/fad946221cec37175e762c399760f54b9de9a9fa...27478af36914f18867ea32cb42db00dba15fffcd)

---
updated-dependencies:
- dependency-name: third_party/abseil-cpp
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
diff --git a/third_party/abseil-cpp b/third_party/abseil-cpp
index fad9462..27478af 160000
--- a/third_party/abseil-cpp
+++ b/third_party/abseil-cpp
@@ -1 +1 @@
-Subproject commit fad946221cec37175e762c399760f54b9de9a9fa
+Subproject commit 27478af36914f18867ea32cb42db00dba15fffcd