chore(deps): bump mcuadros/ofelia from 0.3.20 to 0.3.21 in /cron

Bumps mcuadros/ofelia from 0.3.20 to 0.3.21.

---
updated-dependencies:
- dependency-name: mcuadros/ofelia
  dependency-version: 0.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

cron/Dockerfile

@@ -1,4 +1,4 @@
-FROM mcuadros/ofelia:0.3.20
+FROM mcuadros/ofelia:0.3.21
 LABEL org.label-schema.schema-version="1.0.0-rc1"
 LABEL org.label-schema.vendor="EasyEngine"
 LABEL org.label-schema.name="cron"