[stdlib] remove primary associated type from copyBytes

- this caused an unexpected test failure, will change separately.

Author: glessard

stdlib/public/core/UnsafeBufferPointerSlice.swift

@@ -26,7 +26,9 @@ extension Slice where Base == UnsafeMutableRawBufferPointer {
   ///   be less than or equal to this buffer slice's `count`.
   @inlinable
   @_alwaysEmitIntoClient
-  public func copyBytes(from source: some Collection<UInt8>) {
+  public func copyBytes<C: Collection>(
+    from source: C
+  ) where C.Element == UInt8 {
     let buffer = Base(rebasing: self)
     buffer.copyBytes(from: source)
   }

stdlib/public/core/UnsafeRawBufferPointer.swift.gyb

@@ -534,7 +534,9 @@ extension Unsafe${Mutable}RawBufferPointer {
   /// - Parameter source: A collection of `UInt8` elements. `source.count` must
   ///   be less than or equal to this buffer's `count`.
   @inlinable
-  public func copyBytes(from source: some Collection<UInt8>) {
+  public func copyBytes<C: Collection>(
+    from source: C
+  ) where C.Element == UInt8 {
     guard let position = _position else {
       return
     }