Remove TODO about upstreaming InsertBraces to Chromium clang-format

It looks like we're not gonna be able to upstream this anyway
(https://crbug.com/40247920#comment20), so remove the TODO.

Bug: 40247920
Change-Id: If7e77f0364c008fb3c844481045838b4c5cec707
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/132290
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/.clang-format b/.clang-format
index 30ed2de..b1a81c8 100644
--- a/.clang-format
+++ b/.clang-format
@@ -7,6 +7,4 @@
 # 'int>>' if the file already contains at least one such instance.)
 Standard: Cpp11
 
-# TODO(crbug.com/1392808): Remove when InsertBraces has been upstreamed into
-# the Chromium style (is implied by BasedOnStyle: Chromium).
 InsertBraces: true