Update webmock requirement from <= 3.14.0 to <= 3.19.0

Updates the requirements on [webmock](https://github.com/bblimke/webmock) to permit the latest version.
- [Release notes](https://github.com/bblimke/webmock/releases)
- [Changelog](https://github.com/bblimke/webmock/blob/master/CHANGELOG.md)
- [Commits](bblimke/webmock@v0.9.0...v3.18.1)

---
updated-dependencies:
- dependency-name: webmock
  dependency-type: direct:development
...

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

Author: dependabot[bot]

oauth.gemspec

@@ -66,5 +66,5 @@ Thanks, |7eter l-|. l3oling
   spec.add_development_dependency("rest-client")
   spec.add_development_dependency("rubocop-lts", "~> 18.0")
   spec.add_development_dependency("typhoeus", ">= 0.1.13")
-  spec.add_development_dependency("webmock", "<= 3.14.0")
+  spec.add_development_dependency("webmock", "<= 3.19.0")
 end