fix(brew): move kindle from cask to mas

The `kindle` cask was removed from homebrew-cask, causing brew bundle
to fail for all casks on a fresh Mac.  Amazon Kindle is now distributed
via the Mac App Store.

Author: ebkn

brewfiles/Brewfile-cask

@@ -8,7 +8,6 @@ cask 'slack'
 cask 'google-japanese-ime'
 cask 'visual-studio-code'
 cask 'spotify'
-cask 'kindle'
 cask 'zoom'
 cask 'microsoft-teams'
 cask 'wezterm'

brewfiles/Brewfile-mas

@@ -1,3 +1,4 @@
 mas "Magnet", id: 441258766
 mas "LINE", id: 539883307
 mas "Xcode", id: 497799835
+mas "Amazon Kindle", id: 302584613