Remove sys-proctable dependency, only needed on Windows.

Index: .metadata
--- .metadata.orig
+++ .metadata
@@ -161,7 +161,7 @@ dependencies:
     - - "~>"
       - !ruby/object:Gem::Version
         version: 1.2.2
-  type: :runtime
+  type: :development
   prerelease: false
   version_requirements: !ruby/object:Gem::Requirement
     requirements: