Don't runtime depend on mini_portile2, it's only need for compiling
the extension.

Index: .metadata
--- .metadata.orig
+++ .metadata
@@ -29,7 +29,7 @@ dependencies:
     - - "~>"
       - !ruby/object:Gem::Version
         version: 2.8.2
-  type: :runtime
+  type: :development
   prerelease: false
   version_requirements: !ruby/object:Gem::Requirement
     requirements: