Revert "Add _rg.ps1 to windows zip"

This reverts commit d570f78.

This was reverted because it's blocking a 0.5.0 release. Windows is
foreign to me, and apparently globs are not allowed.

See:
https://ci.appveyor.com/project/BurntSushi/ripgrep/build/1.0.341/job/7o1jqicmtwm7oa00

appveyor.yml

@@ -40,7 +40,6 @@ before_deploy:
   - cargo build --release
   - mkdir staging
   - copy target\release\rg.exe staging
-  - copy target\release\build\ripgrep-*\out\_rg.ps1 staging
   - cd staging
     # release zipfile will look like 'rust-everywhere-v1.2.3-x86_64-pc-windows-msvc'
   - 7z a ../%PROJECT_NAME%-%APPVEYOR_REPO_TAG_NAME%-%TARGET%.zip *