Reduce email chunks

[ArtOfCode-]

The AWS limit of 50 recipients was triggering because we were sending TO one address, BCC 50 others - 51 recipients.

Reduced chunk size to 49, which should solve the problem.

Closes #1724.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.50%. Comparing base (8f917b1) to head (5ffa318).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

Components	Coverage Δ
controllers	68.67% <100.00%> (-0.04%)	⬇️
helpers	79.01% <ø> (ø)
jobs	48.57% <ø> (ø)
models	85.86% <ø> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Oaphi]

For reference, this is the SES quota in question (we use 1 email in TO + N in BCC, hence the adjusted limit):

50 recipients per message.
Note A recipient is any "To", "CC", or "BCC" address.