remove osx stack.yaml

The OSX autobuilder is now using github CI, and can use a current
version of ghc, rather than the old one.

Sponsored-by: Dartmouth College's Datalad project

standalone/osx/stack.yaml

@@ -1,31 +0,0 @@
-flags:
-  git-annex:
-    production: true
-    assistant: true
-    pairing: true
-    torrentparser: true
-    webapp: true
-    magicmime: true
-    dbus: false
-    debuglocks: false
-    benchmark: false
-    networkbsd: false
-    gitlfs: true
-    httpclientrestricted: true
-packages:
-- '.'
-extra-deps:
-- IfElse-0.85
-- aws-0.21.1@@sha256:5290b819bd425f28c736b93a84955ced145bdb631a26d784d1b952e2e0ddc6b8
-- bloomfilter-2.0.1.0
-- filepath-bytestring-1.4.2.1.6
-- sandi-0.5
-- tasty-rerun-1.1.17
-- torrent-10000.1.1
-- git-lfs-1.1.0
-- http-client-restricted-0.0.2
-- http-client-0.5.14
-- magic-1.1
-explicit-setup-deps:
-  git-annex: true
-resolver: lts-13.11