chore: remove the trailing space that fails the mdformat hook

[JustinKovacich]

What

Strips one trailing space from ## Added in CHANGELOG.md.

Why

The mdformat pre-commit hook rewrites that line and exits non-zero when it
modifies a file, so Pre-commit Checks has failed on every pull request since
the initial commit — including Dependabot's open #3. The nit lives on main,
so every branch inherited a red check it didn't cause.

Verification

Full hook suite run locally against the branch — all 13 pass:

Check for useless excludes...........Passed    Lint GitHub Actions workflow files...Passed
trim trailing whitespace.............Passed    zizmor...............................Passed
fix end of files.....................Passed    typos................................Passed
check yaml...........................Passed    Detect hardcoded secrets.............Passed
check for added large files..........Passed    mdformat.............................Passed
check for merge conflicts............Passed    check json..........................Skipped
mixed line ending....................Passed

Follow-up

With this green, Pre-commit Checks can join the required status checks on the
main ruleset, which currently requires the seven Smoke Test jobs.

🤖 Generated with Claude Code