Presubmit cleanup of _EXCLUDED_PATHS

Remove pdf file from _EXCLUDED_PATHS in presubmit. The file no longer
exists.

Change-Id: I740632f3dfb35c490e1cf06bdd2463ea6bac534e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1950728Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Ankit Kumar 🌪️ <ankk@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#721865}

PRESUBMIT.py

@@ -25,7 +25,6 @@ _EXCLUDED_PATHS = (
     r".+_pb2\.py$",
     r".+[\\/]pnacl_shim\.c$",
     r"^gpu[\\/]config[\\/].*_list_json\.cc$",
-    r"^chrome[\\/]browser[\\/]resources[\\/]pdf[\\/]index.js",
     r"tools[\\/]md_browser[\\/].*\.css$",
     # Test pages for Maps telemetry tests.
     r"tools[\\/]perf[\\/]page_sets[\\/]maps_perf_test.*",