Use flatbuffer_py_library name for consistency

Now the naming convention matches other flatbuffer and other python
rules.

Change-Id: Ifa87f95bd3ae3baa5aba0029676fc58d27eaab49
diff --git a/third_party/flatbuffers/build_defs.bzl b/third_party/flatbuffers/build_defs.bzl
index 2ddc65b..2f6c944 100644
--- a/third_party/flatbuffers/build_defs.bzl
+++ b/third_party/flatbuffers/build_defs.bzl
@@ -254,7 +254,7 @@
         compatible_with = compatible_with,
     )
 
-def flatbuffer_python_library(
+def flatbuffer_py_library(
         name,
         srcs,
         namespace,