Center align icon of send box button

[compulim]

Fixes #3672.

Changelog Entry

Fixed

• Fixes #3672. Center the icon of send box buttons vertically and horizontally, by @compulim in PR #3673

Description

The icon is not vertically centered. It is off by 1 pixel.

Design

Specific Changes

• All VRT snapshots are updated
• Some snapshots are deleted because they are orphans

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[corinagum]

TBH I haven't gone through all tests and I'm trusting based off the code changes that test img updates are all valid haha. LGTM

[compulim]

Going through 415 images aren't quick without good tools. And I found a few bugs in our existing snapshots due to retries.

I mean, if we run a test, it failed, we will retry. The snapshot counter will continue to cumulate.

That means, snapshot abc-1-snap.png may fail. It trigger a rerun and will compare against to abc-2-snap.png. So, some snapshot of *-1-snap.png may be "always failing".

Overall test is still verifying our work. But due to this, we lost 1 retry chance as a result because *-1-snap.png is always failing.

Anyway, will look into this issue in the future.

p.s. I also removed all orphans I believe.