Bump github.com/pkg/errors from 0.9.0 to 0.9.1

Bumps [github.com/pkg/errors](https://github.com/pkg/errors) from 0.9.0 to 0.9.1.
- [Release notes](https://github.com/pkg/errors/releases)
- [Commits](https://github.com/pkg/errors/compare/v0.9.0...v0.9.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

go.mod

 module github.com/libp2p/go-reuseport
 
 require (
-	github.com/pkg/errors v0.9.0
+	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.4.0
 	golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e
 )

go.sum

@@ -4,6 +4,8 @@ github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.0 h1:J8lpUdobwIeCI7OiSxHqEwJUKvJwicL5+3v1oe2Yb4k=
 github.com/pkg/errors v0.9.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=