Update thor requirement from ~> 0.20 to >= 0.20, < 2.0

Updates the requirements on [thor](https://github.com/rails/thor) to permit the latest version.
- [Release notes](https://github.com/rails/thor/releases)
- [Commits](rails/thor@v0.20.0...v1.2.2)

---
updated-dependencies:
- dependency-name: thor
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

gemstash.gemspec

@@ -41,7 +41,7 @@ you push your own private gems as well."
   spec.add_runtime_dependency "sequel", "~> 5.0"
   spec.add_runtime_dependency "server_health_check-rack", "~> 0.1"
   spec.add_runtime_dependency "sinatra", ">= 1.4", "< 3.0"
-  spec.add_runtime_dependency "thor", "~> 0.20"
+  spec.add_runtime_dependency "thor", ">= 0.20", "< 2.0"
 
   # Use Redis instead of memcached
   # spec.add_runtime_dependency "redis", "~> 3.3"