Add trailing slash in pdfium_unsafe_buffers_paths.txt.

Prepare for stricter matching in a future version of the plugin. This
also helps avoid stray matches if there were other directories whose
names were prefixed by suppressed directories.

Change-Id: I8303a7e213f50afd8093242800ecaf8027a32b48
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/127290
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Thomas Sepez <tsepez@google.com>

pdfium_unsafe_buffers_paths.txt

diff --git a/pdfium_unsafe_buffers_paths.txt b/pdfium_unsafe_buffers_paths.txt
index 0b8a606..a249d29 100644
--- a/pdfium_unsafe_buffers_paths.txt
+++ b/pdfium_unsafe_buffers_paths.txt
@@ -22,6 +22,6 @@
 -samples/
 -skia/
 -testing/
--third_party
+-third_party/
 -tools/
 -v8/