deps(deps): update axllent/mailpit docker tag to v1.21

[renovate]

This PR contains the following updates:

Package	Update	Change
axllent/mailpit (source)	minor	v1.20 -> v1.21

---

Release Notes

axllent/mailpit (axllent/mailpit)

v1.21

Feature

• Add additional ignored flags to sendmail (#​384)

Chore

• Remove legacy Tags column from message DB table
• Update Go dependencies
• Update node dependencies

Fix

• Fix browser notification request on Edge (#​89)

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 32.82%. Comparing base (6a39745) to head (6f1d0f4).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop      #44   +/-   ##
==========================================
  Coverage      32.82%   32.82%           
  Complexity       119      119           
==========================================
  Files             31       31           
  Lines            463      463           
==========================================
  Hits             152      152           
  Misses           311      311           

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