Merge pull request #63288 from apple/krilnon/unsafe-buffer-pointer-docs

[stdlib] NFC: Restore doc comment for Unsafe[Mutable]BufferPointer

Author: swift-ci

stdlib/public/core/UnsafeBufferPointer.swift.gyb

@@ -29,9 +29,6 @@
 /// instances stored in the underlying memory. However, initializing another
 /// collection with an `${Self}` instance copies the instances out of the
 /// referenced memory and into the new collection.
-// FIXME: rdar://18157434 - until this is fixed, this has to be fixed layout
-// to avoid a hang in Foundation, which has the following setup:
-// struct A { struct B { let x: UnsafeMutableBufferPointer<...> } let b: B }
 @frozen // unsafe-performance
 public struct Unsafe${Mutable}BufferPointer<Element> {