Add webpagereplay/bin into .gitignore

R=bsheedy@chromium.org, tvanderlippe@chromium.org

Bug: 1060399
Change-Id: Id3f5ec43beb735ac44ecf4b4a6723225a9da9a00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2247329Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Arthur Wang <wuwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779399}

third_party/.gitignore

@@ -233,6 +233,7 @@
 /webgl
 /webgl/src
 /webgpu-cts/src
+/webpagereplay/bin
 /webrtc
 /weston/src
 /widevine/cdm/chromeos