flip order of python imports to fix module import error

On some windows machines we were seeing errors
"ImportError: No module named name_style_converter"

This error appears to be caused by the strange interactions in module
imports in generate_bindings.py, potentially some kind of circular
dependency.  However, just changing the order of these imports fixes
the issue.

Change-Id: Icf0a6f36db726ffa25dbbc46fe41b8d8d09f2f5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2070668Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Jeremy Apthorp <jeremya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744076}

third_party/blink/renderer/bindings/scripts/generate_bindings.py

@@ -9,8 +9,8 @@ Runs the bindings code generator for the given tasks.
 import optparse
 import sys
 
-import bind_gen
 import web_idl
+import bind_gen
 
 
 def parse_options():