Bump github.com/imdario/mergo from 0.3.11 to 0.3.12

Bumps [github.com/imdario/mergo](https://github.com/imdario/mergo) from 0.3.11 to 0.3.12.
- [Release notes](https://github.com/imdario/mergo/releases)
- [Commits](darccio/mergo@v0.3.11...0.3.12)

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

go.mod

@@ -18,7 +18,7 @@ require (
 	github.com/giantswarm/to v0.3.0
 	github.com/giantswarm/versionbundle v0.2.0
 	github.com/google/go-cmp v0.5.5
-	github.com/imdario/mergo v0.3.11
+	github.com/imdario/mergo v0.3.12
 	github.com/opencontainers/runc v1.0.0-rc2.0.20190611121236-6cc515888830 // indirect
 	github.com/prometheus/client_golang v1.9.0
 	github.com/spf13/afero v1.5.1