Removing third_party/abseil-cpp. (#6260)

diff --git a/.gitmodules b/.gitmodules
index 049519e..e3a9b26 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,3 @@
-[submodule "third_party/abseil-cpp"]
-	path = third_party/abseil-cpp
-	url = https://github.com/abseil/abseil-cpp.git
 [submodule "third_party/googletest"]
 	path = third_party/googletest
 	url = https://github.com/google/googletest.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1db2b1..eacfd9d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -436,7 +436,6 @@
 if(${IREE_ENABLE_THREADING})
   add_subdirectory(third_party/benchmark EXCLUDE_FROM_ALL)
   add_subdirectory(third_party/cpuinfo EXCLUDE_FROM_ALL)
-  add_subdirectory(third_party/abseil-cpp EXCLUDE_FROM_ALL)
 endif()
 add_subdirectory(third_party/flatcc EXCLUDE_FROM_ALL)
 add_subdirectory(third_party/vulkan_headers EXCLUDE_FROM_ALL)
diff --git a/SUBMODULE_VERSIONS.txt b/SUBMODULE_VERSIONS.txt
index e97b241..ff25a63 100644
--- a/SUBMODULE_VERSIONS.txt
+++ b/SUBMODULE_VERSIONS.txt
@@ -1,4 +1,3 @@
-6f9d96a1f41439ac172ee2ef7ccd8edf0e5d068c third_party/abseil-cpp
 39c8d58a76ce7c3398786ee96a452668e8392af7 third_party/benchmark
 5916273f79a21551890fd3d56fc5375a78d1598d third_party/cpuinfo
 32aabef14ccc0e3ac15602c99476d25dcd230d19 third_party/flatcc
diff --git a/docs/developers/developing_iree/repository_management.md b/docs/developers/developing_iree/repository_management.md
index cd96cc1..9c7dfdf 100644
--- a/docs/developers/developing_iree/repository_management.md
+++ b/docs/developers/developing_iree/repository_management.md
@@ -101,7 +101,6 @@
 the repository root. Here is an example:
 
 ```text
-6ec136281086b71da32b5fb068bd6e46b78a5c79 third_party/abseil-cpp
 309de5988eb949a27e077a24a1d83c0687d10d57 third_party/benchmark
 97f3aa91746a7d207513a73725e92cee7c35bb87 third_party/flatbuffers
 f2fb48c3b3d79a75a88a99fba6576b25d42ec528 third_party/googletest
diff --git a/third_party/abseil-cpp b/third_party/abseil-cpp
deleted file mode 160000
index 6f9d96a..0000000
--- a/third_party/abseil-cpp
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 6f9d96a1f41439ac172ee2ef7ccd8edf0e5d068c