Bump github.com/mailgun/mailgun-go/v4 from 4.18.1 to 4.18.5 (#531)

Bumps [github.com/mailgun/mailgun-go/v4](https://github.com/mailgun/mailgun-go) from 4.18.1 to 4.18.5.
- [Release notes](https://github.com/mailgun/mailgun-go/releases)
- [Changelog](https://github.com/mailgun/mailgun-go/blob/master/CHANGELOG)
- [Commits](mailgun/mailgun-go@v4.18.1...v4.18.5)

---
updated-dependencies:
- dependency-name: github.com/mailgun/mailgun-go/v4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

go.mod

@@ -7,7 +7,7 @@ require (
 	github.com/go-openapi/swag v0.23.0
 	github.com/google/certificate-transparency-go v1.2.2
 	github.com/google/go-github/v65 v65.0.0
-	github.com/mailgun/mailgun-go/v4 v4.18.1
+	github.com/mailgun/mailgun-go/v4 v4.18.5
 	github.com/migueleliasweb/go-github-mock v1.1.0
 	github.com/mocktools/go-smtp-mock/v2 v2.3.1
 	github.com/sendgrid/sendgrid-go v3.16.0+incompatible

go.sum

@@ -135,8 +135,8 @@ github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0V
 github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
 github.com/mailgun/errors v0.3.0 h1:g8R8lodkwqk5WIVMAClyUqt0PSd5JTVgobB+H7C2sLs=
 github.com/mailgun/errors v0.3.0/go.mod h1:+ltknP+jhv3gZ1StKY6ugoQECcPxDCaSdmYesqTZcLQ=
-github.com/mailgun/mailgun-go/v4 v4.18.1 h1:ShNH/wzj7albTF/6le011FF+DGMd3azcSKL4iO9AgeI=
-github.com/mailgun/mailgun-go/v4 v4.18.1/go.mod h1:+d4FCswFAukgYc1XtKK2IxOYaVxjVm8AN2z/5TBiT8M=
+github.com/mailgun/mailgun-go/v4 v4.18.5 h1:wZnTutW/fzxNyJVBMa6O4LLGW/hO+IGfKpuqBT4nbVs=
+github.com/mailgun/mailgun-go/v4 v4.18.5/go.mod h1:+d4FCswFAukgYc1XtKK2IxOYaVxjVm8AN2z/5TBiT8M=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=