Fix Indices.BulkAsync summary

[jumc]

Description

Update Indices.BulkAsync summary with the correct API name

Issues Resolved

Closes [#715].

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[Xtansia]

Thanks for catching this and making a PR, there's just a few other things to fix in the comments.

It looks like the DCO check (checks for Signed-off-by:) is failing as the Committer, Author and Signed-off-by details of the commit don't match, could you please look into amending them?

[opensearch-trigger-bot]

The backport to 1.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-1.x 1.x
# Navigate to the new working tree
cd .worktrees/backport-1.x
# Create a new branch
git switch --create backport/backport-717-to-1.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c2fdd5d1df4929000249d07ccdf2c8b21fd2fde6
# Push it to GitHub
git push --set-upstream origin backport/backport-717-to-1.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.x

Then, create a pull request where the base branch is 1.x and the compare/head branch is backport/backport-717-to-1.x.