Update harfbuzz to 7.3.0

[mattleibow]

Updating more of the externals.

[github-actions]

The backport to release/2.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-release/2.x release/2.x
# Navigate to the new working tree
cd .worktrees/backport-release/2.x
# Create a new branch
git switch --create backport/pr-104-to-release/2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 3c98e7cdf210a560c614933893b4f5566f0b83cc
# Push it to GitHub
git push --set-upstream origin backport/pr-104-to-release/2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release/2.x

Then, create a pull request where the base branch is release/2.x and the compare/head branch is backport/pr-104-to-release/2.x.