Update rspec requirement from ~> 3.11.0 to ~> 3.12.0

Updates the requirements on [rspec](https://github.com/rspec/rspec-metagem) to permit the latest version.
- [Release notes](https://github.com/rspec/rspec-metagem/releases)
- [Commits](https://github.com/rspec/rspec-metagem/compare/v3.11.0...v3.12.0)

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

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

wpscan.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'bundler',             '>= 1.6'
   s.add_development_dependency 'memory_profiler',     '~> 1.0.0'
   s.add_development_dependency 'rake',                '~> 13.0'
-  s.add_development_dependency 'rspec',               '~> 3.11.0'
+  s.add_development_dependency 'rspec',               '~> 3.12.0'
   s.add_development_dependency 'rspec-its',           '~> 1.3.0'
   s.add_development_dependency 'rubocop',             '~> 1.26.0'
   s.add_development_dependency 'rubocop-performance', '~> 1.13.0'