build(deps): bump github.com/emersion/go-smtp from 0.20.2 to 0.21.1

Bumps [github.com/emersion/go-smtp](https://github.com/emersion/go-smtp) from 0.20.2 to 0.21.1.
- [Release notes](https://github.com/emersion/go-smtp/releases)
- [Commits](emersion/go-smtp@v0.20.2...v0.21.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

go.mod

@@ -5,7 +5,7 @@ go 1.21
 require (
 	github.com/creasty/defaults v1.7.0
 	github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43
-	github.com/emersion/go-smtp v0.20.2
+	github.com/emersion/go-smtp v0.21.1
 	github.com/goccy/go-yaml v1.11.3
 	github.com/google/uuid v1.6.0
 	github.com/icinga/icingadb v1.1.1-0.20230418113126-7c4b947aad3a
@@ -16,6 +16,7 @@ require (
 	go.uber.org/zap v1.27.0
 	golang.org/x/crypto v0.22.0
 	golang.org/x/exp v0.0.0-20220613132600-b0d781184e0d
+	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 )
 
 require (
@@ -41,7 +42,6 @@ require (
 	github.com/ssor/bom v0.0.0-20170718123548-6386211fdfcf // indirect
 	go.uber.org/multierr v1.10.0 // indirect
 	golang.org/x/net v0.21.0 // indirect
-	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
 	golang.org/x/sys v0.19.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect

go.sum

@@ -11,8 +11,8 @@ github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cu
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
 github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43 h1:hH4PQfOndHDlpzYfLAAfl63E8Le6F2+EL/cdhlkyRJY=
 github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/emersion/go-smtp v0.20.2 h1:peX42Qnh5Q0q3vrAnRy43R/JwTnnv75AebxbkTL7Ia4=
-github.com/emersion/go-smtp v0.20.2/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
+github.com/emersion/go-smtp v0.21.1 h1:VQeZSZAKk8ueYii1yR5Zalmy7jI287eWDUqSaJ68vRM=
+github.com/emersion/go-smtp v0.21.1/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/fatih/color v1.13.0 h1:8LOYc1KYPPmyKMuN8QV2DNRWNbLo6LZ0iLs8+mlH53w=
 github.com/fatih/color v1.13.0/go.mod h1:kLAiJbzzSOZDVNGyDpeOxJ47H46qBXwg5ILebYFFOfk=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=