build(deps): Bump github.com/mitchellh/mapstructure from 1.1.2 to 1.4.0

Bumps [github.com/mitchellh/mapstructure](https://github.com/mitchellh/mapstructure) from 1.1.2 to 1.4.0.
- [Release notes](https://github.com/mitchellh/mapstructure/releases)
- [Changelog](https://github.com/mitchellh/mapstructure/blob/master/CHANGELOG.md)
- [Commits](mitchellh/mapstructure@v1.1.2...v1.4.0)

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

go.mod

@@ -4,7 +4,7 @@ go 1.15
 
 require (
 	github.com/google/uuid v1.1.2
-	github.com/mitchellh/mapstructure v1.1.2
+	github.com/mitchellh/mapstructure v1.4.0
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.9.0
 	github.com/prometheus/common v0.15.0

go.sum

@@ -189,6 +189,8 @@ github.com/mitchellh/iochan v1.0.0/go.mod h1:JwYml1nuB7xOzsp52dPpHFffvOCDupsG0Qu
 github.com/mitchellh/mapstructure v0.0.0-20160808181253-ca63d7c062ee/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
 github.com/mitchellh/mapstructure v1.1.2 h1:fmNYVwqnSfB9mZU6OS2O6GsXM+wcskZDuKQzvN1EDeE=
 github.com/mitchellh/mapstructure v1.1.2/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
+github.com/mitchellh/mapstructure v1.4.0 h1:7ks8ZkOP5/ujthUsT07rNv+nkLXCQWKNHuwzOAesEks=
+github.com/mitchellh/mapstructure v1.4.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=