Bump github.com/gosimple/slug from 1.14.0 to 1.15.0

Bumps [github.com/gosimple/slug](https://github.com/gosimple/slug) from 1.14.0 to 1.15.0.
- [Release notes](https://github.com/gosimple/slug/releases)
- [Commits](https://github.com/gosimple/slug/compare/v1.14.0...v1.15.0)

---
updated-dependencies:
- dependency-name: github.com/gosimple/slug
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

go.mod

@@ -19,7 +19,7 @@ require (
 	github.com/gorilla/mux v1.8.1
 	github.com/gorilla/schema v1.4.1
 	github.com/gorilla/sessions v1.3.0
-	github.com/gosimple/slug v1.14.0
+	github.com/gosimple/slug v1.15.0
 	github.com/guregu/null v4.0.0+incompatible
 	github.com/hashicorp/go-multierror v1.1.1
 	github.com/ikeikeikeike/go-sitemap-generator/v2 v2.0.2

go.sum

@@ -92,8 +92,8 @@ github.com/gorilla/securecookie v1.1.2 h1:YCIWL56dvtr73r6715mJs5ZvhtnY73hBvEF8kX
 github.com/gorilla/securecookie v1.1.2/go.mod h1:NfCASbcHqRSY+3a8tlWJwsQap2VX5pwzwo4h3eOamfo=
 github.com/gorilla/sessions v1.3.0 h1:XYlkq7KcpOB2ZhHBPv5WpjMIxrQosiZanfoy1HLZFzg=
 github.com/gorilla/sessions v1.3.0/go.mod h1:ePLdVu+jbEgHH+KWw8I1z2wqd0BAdAQh/8LRvBeoNcQ=
-github.com/gosimple/slug v1.14.0 h1:RtTL/71mJNDfpUbCOmnf/XFkzKRtD6wL6Uy+3akm4Es=
+github.com/gosimple/slug v1.15.0 h1:wRZHsRrRcs6b0XnxMUBM6WK1U1Vg5B0R7VkIf1Xzobo=
-github.com/gosimple/slug v1.14.0/go.mod h1:UiRaFH+GEilHstLUmcBgWcI42viBN7mAb818JrYOeFQ=
+github.com/gosimple/slug v1.15.0/go.mod h1:UiRaFH+GEilHstLUmcBgWcI42viBN7mAb818JrYOeFQ=
 github.com/gosimple/unidecode v1.0.1 h1:hZzFTMMqSswvf0LBJZCZgThIZrpDHFXux9KeGmn6T/o=
 github.com/gosimple/unidecode v1.0.1/go.mod h1:CP0Cr1Y1kogOtx0bJblKzsVWrqYaqfNOnHzpgWw4Awc=
 github.com/guregu/null v4.0.0+incompatible h1:4zw0ckM7ECd6FNNddc3Fu4aty9nTlpkkzH7dPn4/4Gw=