Delete unused files.

python/google/protobuf/internal/import_test_package/BUILD

-# Description:
-#   An example package that contains nested protos that are imported from
-#   __init__.py. See testPackageInitializationImport in reflection_test.py for
-#   details.
-
-package(
-    default_visibility = ["//net/proto2/python/internal:__pkg__"],
-)
-
-proto_library(
-    name = "inner_proto",
-    srcs = ["inner.proto"],
-    py_api_version = 2,
-)
-
-proto_library(
-    name = "outer_proto",
-    srcs = ["outer.proto"],
-    py_api_version = 2,
-    deps = [":inner_proto"],
-)
-
-py_library(
-    name = "import_test_package",
-    srcs = ["__init__.py"],
-    deps = [":outer_proto"],
-)