Fix the name of `gofmt` on Windows in `go_presubmit_support.py`

Bug: chromium:343519239
Change-Id: Ic227da4be398e17e527c4a867babe340a09f6508
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/211974
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
diff --git a/go_presubmit_support.py b/go_presubmit_support.py
index f3dc997..bb502d2 100644
--- a/go_presubmit_support.py
+++ b/go_presubmit_support.py
@@ -42,7 +42,7 @@
 def gofmt_path(input_api):
     gofmt = input_api.os_path.join(go_bin_path(input_api), 'gofmt')
     if input_api.is_windows:
-        go += '.exe'
+        gofmt += '.exe'
     return gofmt