Merge pull request #71009 from nate-chandler/bitwise-copyable-gating

[BitwiseCopyable] Remove gating from protocol declaration.

Author: nate-chandler

stdlib/public/core/Misc.swift

@@ -182,6 +182,4 @@ func _rethrowsViaClosure(_ fn: () throws -> ()) rethrows {
 @_marker public protocol Escapable {}
 #endif
 
-#if $BitwiseCopyable
 @_marker public protocol _BitwiseCopyable {}
-#endif

stdlib/public/core/Optional.swift

@@ -783,6 +783,4 @@ extension Optional: _ObjectiveCBridgeable {
 
 extension Optional: Sendable where Wrapped: Sendable { }
 
-#if $BitwiseCopyable
 extension Optional: _BitwiseCopyable where Wrapped: _BitwiseCopyable { }
-#endif