Make roll_harfbuzz.sh work properly on Mac.

On Mac `find` by default interprets the first parameter literally as a
directory string and does not normalize the resulting file names the way
`find` does on Linux. Remove the unnecessary trailing '/' so that both
Mac and Linux versions produce the expected output.

Change-Id: I0f06d6025ce7eb545a5fbdab7686403bbebc80b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3384285
Auto-Submit: Ben Wagner <bungeman@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/main@{#958489}

third_party/harfbuzz-ng/roll-harfbuzz.sh

@@ -53,7 +53,7 @@ check_all_files_are_categorized() {
     CDPATH= && cd -- "$(dirname -- "$0")" &&
 
     HB_SOURCE_MISSING=false &&
-    find src/src/ -type f \( -name "hb-*.cc" -o -name "hb-*.h" -o -name "hb-*.hh" \) | while read HB_SOURCE
+    find src/src -type f \( -name "hb-*.cc" -o -name "hb-*.h" -o -name "hb-*.hh" \) | while read HB_SOURCE
     do
       if ! grep -qF "$HB_SOURCE" BUILD.gn; then
         if ! ${HB_SOURCE_MISSING}; then