build(deps): bump github.com/spf13/viper from 1.14.0 to 1.15.0 in /proxy (#74)

Bumps [github.com/spf13/viper](https://github.com/spf13/viper) from 1.14.0 to 1.15.0.
- [Release notes](https://github.com/spf13/viper/releases)
- [Commits](https://github.com/spf13/viper/compare/v1.14.0...v1.15.0)

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

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Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

proxy/go.mod

@@ -7,5 +7,5 @@ require (
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/gorilla/handlers v1.5.1
 	github.com/spf13/pflag v1.0.5
-	github.com/spf13/viper v1.14.0
+	github.com/spf13/viper v1.15.0
 )