ReleaseNotes: remove another in-progress warning
ReleaseNotes: remove another in-progress warning

git-svn-id: 04729e557c999f6eb47c5e86934ec5cfbcf85584@312152 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang