Update Python Flatbuffer contents by removing redundant files

PiperOrigin-RevId: 360260751
Change-Id: I6685377430f07a116165edb2f5270ae06fa952c0

third_party/flatbuffers/BUILD.bazel

@@ -103,8 +103,6 @@ cc_library(
     visibility = ["//visibility:public"],
 )
 
-# Note: Don't include "flexbuffers.py" as it's not available in the latest
-# pip package (version 1.12.0) and causes failures in internal pip tests.
 flatbuffer_py_strip_prefix_srcs(
     name = "flatbuffer_py_strip_prefix",
     srcs = [

third_party/flatbuffers/build_defs.bzl

@@ -375,7 +375,7 @@ def flatbuffer_py_strip_prefix_srcs(name, srcs = [], strip_prefix = ""):
             name = name + "_" + src.replace(".", "_").replace("/", "_"),
             srcs = [src],
             outs = [src.replace(strip_prefix, "")],
-            cmd = "mv $< $@",
+            cmd = "cp $< $@",
         )
 
 def _concat_flatbuffer_py_srcs_impl(ctx):