Remove tensorflow submodule in favor of bazel fetch. (#8085)

* Remove tensorflow submodule in favor of bazel fetch.

Now that integrations/tensorflow is isolated from the rest of IREE, we can just have bazel fetch tensorflow and leave git out of it. Will see how the ergonomics of this is.
diff --git a/.gitmodules b/.gitmodules
index a40d532..7b053e2 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,9 +4,6 @@
 [submodule "third_party/llvm-project"]
 	path = third_party/llvm-project
 	url = https://github.com/llvm/llvm-project.git
-[submodule "third_party/tensorflow"]
-	path = third_party/tensorflow
-	url = https://github.com/tensorflow/tensorflow.git
 [submodule "third_party/vulkan_headers"]
 	path = third_party/vulkan_headers
 	url = https://github.com/KhronosGroup/Vulkan-Headers.git
diff --git a/SUBMODULE_VERSIONS.txt b/SUBMODULE_VERSIONS.txt
index bdaec94..e437363 100644
--- a/SUBMODULE_VERSIONS.txt
+++ b/SUBMODULE_VERSIONS.txt
@@ -11,7 +11,6 @@
 e9cc6403341baf0edd430a4027b074d0a06b782f third_party/spirv_cross
 d53b49635b7484e86959608a65a64d8121e6a385 third_party/spirv_headers
 af1a5bc352164740c1cc1354942b1c6b72eacb8a third_party/stblib
-baa6d31a0af6adb7058e229001931a1fdd6f81bb third_party/tensorflow
 058e89011fceca912d43638ebb6b85992147fcfe third_party/tracy
 9e62d027636cd7210f60d934f56107ed6e1579b8 third_party/vulkan_headers
 5c8b3ba955f0dbb30d18afc420f3a38adc779231 third_party/vulkan_memory_allocator
diff --git a/integrations/tensorflow/WORKSPACE b/integrations/tensorflow/WORKSPACE
index 54e64a2..9ab0803 100644
--- a/integrations/tensorflow/WORKSPACE
+++ b/integrations/tensorflow/WORKSPACE
@@ -5,9 +5,14 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 """Adds a local dependency on tensorflow."""
 
-local_repository(
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+
+TENSORFLOW_COMMIT = "baa6d31a0af6adb7058e229001931a1fdd6f81bb"
+
+git_repository(
     name = "org_tensorflow",
-    path = "../../third_party/tensorflow",
+    commit = TENSORFLOW_COMMIT,
+    remote = "https://github.com/tensorflow/tensorflow.git",
 )
 
 # Import all of the tensorflow dependencies.
diff --git a/third_party/tensorflow b/third_party/tensorflow
deleted file mode 160000
index baa6d31..0000000
--- a/third_party/tensorflow
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit baa6d31a0af6adb7058e229001931a1fdd6f81bb