Update comments for expressions split due to slow type checking.
Update comments for expressions split due to slow type checking.

Add the SR number to the comment. I've also updated the SR to point back
to the PR for the work-around so that we know to revert the change when
the issue is resolved.

johnno1962b/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,parkera/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,e78l/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,apple/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,alblue/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,apple/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,alblue/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,parkera/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,alblue/swift-corelibs-foundation,apple/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,parkera/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,e78l/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation