Remove sys-proctable dependency, only needed on Windows.

Remove pessimistic version restriction on nokogiri dependency.

Index: .metadata
--- .metadata.orig
+++ .metadata
@@ -176,7 +176,7 @@ dependencies:
     - - "<"
       - !ruby/object:Gem::Version
         version: 1.4.0
-  type: :runtime
+  type: :development
   prerelease: false
   version_requirements: !ruby/object:Gem::Requirement
     requirements:
