remove python-numpy packages (#52)

- since numpy will be installed by `pip install` only

diff --git a/container/experimental/rbe-ubuntu16_04/BUILD b/container/experimental/rbe-ubuntu16_04/BUILD
index d37e742..bc11d6c 100644
--- a/container/experimental/rbe-ubuntu16_04/BUILD
+++ b/container/experimental/rbe-ubuntu16_04/BUILD
@@ -121,7 +121,6 @@
     installation_cleanup_commands = PYTHON_CLEANUP_COMMANDS,
     packages = [
         "python-dev",
-        "python-numpy",
         "python-setuptools",
         "python3-dev",
     ],
diff --git a/container/rbe-debian8/BUILD b/container/rbe-debian8/BUILD
index b05462d..734adca 100644
--- a/container/rbe-debian8/BUILD
+++ b/container/rbe-debian8/BUILD
@@ -124,7 +124,6 @@
     installation_cleanup_commands = PYTHON_CLEANUP_COMMANDS,
     packages = [
         "python-dev",
-        "python-numpy",
         "python-setuptools",
         "python3-dev",
     ],