Bump github.com/gorilla/mux from 1.7.0 to 1.7.3 in /api_mock

Bumps [github.com/gorilla/mux](https://github.com/gorilla/mux) from 1.7.0 to 1.7.3.
- [Release notes](https://github.com/gorilla/mux/releases)
- [Commits](gorilla/mux@v1.7.0...v1.7.3)

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

Author: dependabot-preview[bot]

api_mock/go.mod

@@ -5,7 +5,7 @@ go 1.12
 require (
 	github.com/bukalapak/snowboard v1.7.0
 	github.com/cweill/gotests v1.5.3 // indirect
-	github.com/gorilla/mux v1.7.0
+	github.com/gorilla/mux v1.7.3
 	github.com/gosimple/slug v1.4.2 // indirect
 	github.com/rainycape/unidecode v0.0.0-20150907023854-cb7f23ec59be // indirect
 	github.com/stretchr/testify v1.3.0 // indirect

api_mock/go.sum

@@ -6,6 +6,8 @@ github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/gorilla/mux v1.7.0 h1:tOSd0UKHQd6urX6ApfOn4XdBMY6Sh1MfxV3kmaazO+U=
 github.com/gorilla/mux v1.7.0/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
+github.com/gorilla/mux v1.7.3 h1:gnP5JzjVOuiZD07fKKToCAOjS0yOpj/qPETTXCCS6hw=
+github.com/gorilla/mux v1.7.3/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
 github.com/gosimple/slug v1.4.2 h1:jDmprx3q/9Lfk4FkGZtvzDQ9Cj9eAmsjzeQGp24PeiQ=
 github.com/gosimple/slug v1.4.2/go.mod h1:ER78kgg1Mv0NQGlXiDe57DpCyfbNywXXZ9mIorhxAf0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=