Fix broken brew cask alfred link

[mecca831]

brew cask alfred link is broken because features.defaultresults.scope is a string instead of a dictionary:

[00:13]:) ~ $ brew cask alfred link
==> Successfully linked Alfred to homebrew-cask.
[00:13]:) ~ $ brew cask alfred status
==> Alfred is not linked to homebrew-cask.
[00:15]:) ~ $ defaults read com.runningwithcrayons.Alfred-Preferences
{
    NSNavLastRootDirectory = "~/Documents";
    NSNavPanelExpandedSizeForOpenMode = "{750, 480}";
    "NSWindow Frame alfredpreferences" = "0 56 1383 822 0 0 1440 878 ";
    "features.defaultresults.scope" = "('/Applications','/Applications/Xcode.app/Contents/Applications','/Developer/Applications','/Library/PreferencePanes','/System/Library/PreferencePanes','~/Library/Caches/Metadata/','~/Library/Mobile Documents/','~/Library/PreferencePanes','/opt/homebrew-cask/Caskroom')";
    lastTab = features;
    lastTabBuild = 227;
    lastTabTS = "415265223.980409";
    version = "2.1.1";
}

• Remove quotes from defaults write args. With quotes the value is
  written as a string instead of a dictionary, which breaks the search
  scope in alfred.
• Make the default scope consistent with alfred default

[rolandwalker]

Thanks!

This seems to have been broken since #2624 (release 0.29.0). And the tests didn't catch it because the tests were wrong. Apologies if the bug caused you any inconvenience.