Patch out mini_portile2 requirement, we're not using it at build time.

Index: ruby-gpgme/metadata.yml
===================================================================
--- ruby-gpgme.orig/metadata.yml
+++ ruby-gpgme/metadata.yml
@@ -12,20 +12,6 @@ cert_chain: []
 date: 2016-01-19 00:00:00.000000000 Z
 dependencies:
 - !ruby/object:Gem::Dependency
-  name: mini_portile2
-  requirement: !ruby/object:Gem::Requirement
-    requirements:
-    - - "~>"
-      - !ruby/object:Gem::Version
-        version: 2.1.0
-  type: :runtime
-  prerelease: false
-  version_requirements: !ruby/object:Gem::Requirement
-    requirements:
-    - - "~>"
-      - !ruby/object:Gem::Version
-        version: 2.1.0
-- !ruby/object:Gem::Dependency
   name: mocha
   requirement: !ruby/object:Gem::Requirement
     requirements:
