build(deps): bump third_party/abseil-cpp from `770d078` to `b8f2b2c` (#2345)

Bumps [third_party/abseil-cpp](https://github.com/abseil/abseil-cpp) from `770d078` to `b8f2b2c`.
- [Release notes](https://github.com/abseil/abseil-cpp/releases)
- [Commits](https://github.com/abseil/abseil-cpp/compare/770d078368f66da606ad98187f33fbc5b8cdd3ae...b8f2b2c6cf362acc30ebb581dfc43d44f73bdf23)

---
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 770d078..b8f2b2c 160000
--- a/third_party/abseil-cpp
+++ b/third_party/abseil-cpp
@@ -1 +1 @@
-Subproject commit 770d078368f66da606ad98187f33fbc5b8cdd3ae
+Subproject commit b8f2b2c6cf362acc30ebb581dfc43d44f73bdf23