Bump github.com/spf13/afero from 1.6.0 to 1.9.3

Bumps [github.com/spf13/afero](https://github.com/spf13/afero) from 1.6.0 to 1.9.3.
- [Release notes](https://github.com/spf13/afero/releases)
- [Commits](https://github.com/spf13/afero/compare/v1.6.0...v1.9.3)

---
updated-dependencies:
- dependency-name: github.com/spf13/afero
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

go.mod

@@ -10,9 +10,8 @@ require (
 	github.com/kr/text v0.2.0 // indirect
 	github.com/mmcdole/gofeed v1.1.3
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
-	github.com/spf13/afero v1.6.0
+	github.com/spf13/afero v1.9.3
 	github.com/stretchr/testify v1.8.1
-	golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e // indirect
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 	gopkg.in/yaml.v2 v2.4.0
 )