chore(deps): bump github.com/emersion/go-smtp from 0.16.0 to 0.18.1 (#1771)

Bumps [github.com/emersion/go-smtp](https://github.com/emersion/go-smtp) from 0.16.0 to 0.18.1.
- [Release notes](https://github.com/emersion/go-smtp/releases)
- [Commits](https://github.com/emersion/go-smtp/compare/v0.16.0...v0.18.1)

---
updated-dependencies:
- dependency-name: github.com/emersion/go-smtp
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.sum

@@ -344,8 +344,8 @@ github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+m
 github.com/elazarl/goproxy v0.0.0-20230731152917-f99041a5c027 h1:1L0aalTpPz7YlMxETKpmQoWMBkeiuorElZIXoNmgiPE=
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21 h1:OJyUGMJTzHTd1XQp98QTaHernxMYzRaOasRir9hUlFQ=
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/emersion/go-smtp v0.16.0 h1:eB9CY9527WdEZSs5sWisTmilDX7gG+Q/2IdRcmubpa8=
-github.com/emersion/go-smtp v0.16.0/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
+github.com/emersion/go-smtp v0.18.1 h1:4DFV0jxKhq0Gqt/Br3BRHyKZy5TStk6NIMHAx6GE/LA=
+github.com/emersion/go-smtp v0.18.1/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/emicklei/go-restful/v3 v3.8.0 h1:eCZ8ulSerjdAiaNpF7GxXIE7ZCMo1moN1qX+S609eVw=
 github.com/emirpasic/gods v1.18.1 h1:FXtiHYKDGKCW2KzwZKx0iC0PQmdlorYgdFG9jPXJ1Bc=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=