Fix CompletionSuggester based on spec fixes.

[stevejgordon]

Fixes #7454.

[github-actions]

The backport to 8.0 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-8.0 8.0
# Navigate to the new working tree
cd .worktrees/backport-8.0
# Create a new branch
git switch --create backport-7456-to-8.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 85e79de87d561d0cfd773ea2eb064070199a35a7
# Push it to GitHub
git push --set-upstream origin backport-7456-to-8.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.0

Then, create a pull request where the base branch is 8.0 and the compare/head branch is backport-7456-to-8.0.