build(deps): Bump github.com/DeRuina/timberjack from 1.3.9 to 1.4.0

Bumps [github.com/DeRuina/timberjack](https://github.com/DeRuina/timberjack) from 1.3.9 to 1.4.0.
- [Release notes](https://github.com/DeRuina/timberjack/releases)
- [Changelog](https://github.com/DeRuina/timberjack/blob/main/CHANGELOG.md)
- [Commits](https://github.com/DeRuina/timberjack/compare/v1.3.9...v1.4.0)

---
updated-dependencies:
- dependency-name: github.com/DeRuina/timberjack
  dependency-version: 1.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

go.mod

@@ -1,7 +1,7 @@
 module github.com/decke/smtprelay
 
 require (
-	github.com/DeRuina/timberjack v1.3.9
+	github.com/DeRuina/timberjack v1.4.0
 	github.com/chrj/smtpd v0.3.1
 	github.com/fsnotify/fsnotify v1.9.0
 	github.com/google/uuid v1.6.0

go.sum

@@ -1,5 +1,5 @@
-github.com/DeRuina/timberjack v1.3.9 h1:6UXZ1I7ExPGTX/1UNYawR58LlOJUHKBPiYC7WQ91eBo=
-github.com/DeRuina/timberjack v1.3.9/go.mod h1:RLoeQrwrCGIEF8gO5nV5b/gMD0QIy7bzQhBUgpp1EqE=
+github.com/DeRuina/timberjack v1.4.0 h1:Ipw9KjS/6K6A9D1xdhWebYJFqdQez5gXwfzmeKOroqE=
+github.com/DeRuina/timberjack v1.4.0/go.mod h1:RLoeQrwrCGIEF8gO5nV5b/gMD0QIy7bzQhBUgpp1EqE=
 github.com/chrj/smtpd v0.3.1 h1:kogHFkbFdKaoH3bgZkqNC9uVtKYOFfM3uV3rroBdooE=
 github.com/chrj/smtpd v0.3.1/go.mod h1:JtABvV/LzvLmEIzy0NyDnrfMGOMd8wy5frAokwf6J9Q=
 github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=