[abseil] Abseil has moved location in //third_party

Bug: 468025056
Change-Id: Ibb3a35ba1a2fba17840b9894ba7f14af716caba7
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/grpc/+/1544980
Reviewed-by: Alex Pankhurst <pankhurst@google.com>
Reviewed-by: Anivia Li <aniviali@google.com>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index aaa40fe..dd7296e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -46,7 +46,7 @@
     "//third_party/cares/include",
     "./third_party/upb",
     "./third_party/xxhash",
-    "//third_party/abseil-cpp",
+    "//third_party/abseil-cpp/src",
   ]
 
   defines = [