Require go-viper/mapstructure/v2 instead of mitchellh/mapstructure

Proprietary

Bring the go.mod require into line with what the source imports: repoint github.com/mitchellh/mapstructure at github.com/go-viper/mapstructure/v2 v2.5.0 once nothing imports the unmaintained module any more, and require both while a file naming the dropped mapstructure.Error still does. Does not sync go.sum, so a go mod tidy is still needed to complete resolution.

org.openrewrite.golang.migration.UpdateMapstructureDependency
mod run . --recipe=org.openrewrite.golang.migration.UpdateMapstructureDependency

Install it once, then run it on every repository under the current directory. New to the Moderne CLI? Set it up.