Revert "update protobuf version to 3.11.4 to match tensorflow-nightly (#1320)"

This reverts commit 07d833f.

Author: vnghia

WORKSPACE

@@ -12,14 +12,11 @@ cuda_configure(name = "local_config_cuda")
 
 http_archive(
     name = "com_google_protobuf",
-    patch_cmds = [
-        """sed -i.bak 's/@six\\/\\/:six/\\/\\/external:six/g' BUILD""",
-    ],
-    sha256 = "9748c0d90e54ea09e5e75fb7fac16edce15d2028d4356f32211cfa3c0e956564",
-    strip_prefix = "protobuf-3.11.4",
+    sha256 = "cfcba2df10feec52a84208693937c17a4b5df7775e1635c1e3baffc487b24c9b",
+    strip_prefix = "protobuf-3.9.2",
     urls = [
-        "https://storage.googleapis.com/mirror.tensorflow.org/github.com/protocolbuffers/protobuf/archive/v3.11.4.zip",
-        "https://github.com/protocolbuffers/protobuf/archive/v3.11.4.zip",
+        "https://storage.googleapis.com/mirror.tensorflow.org/github.com/protocolbuffers/protobuf/archive/v3.9.2.zip",
+        "https://github.com/protocolbuffers/protobuf/archive/v3.9.2.zip",
     ],
 )