Fix size used for vectorization check in BitArray (#111558) (#111564)

Co-authored-by: Eirik Tsarpalis <[email protected]>

Author: AnsBalin

src/libraries/System.Collections/src/System/Collections/BitArray.cs

@@ -885,7 +885,7 @@ public unsafe void CopyTo(Array array, int index)
                         }
                     }
                 }
-                else if (Ssse3.IsSupported && ((uint)m_length >= Vector512<byte>.Count * 2u))
+                else if (Ssse3.IsSupported && ((uint)m_length >= Vector128<byte>.Count * 2u))
                 {
                     Vector128<byte> lowerShuffleMask = lowerShuffleMask_CopyToBoolArray;
                     Vector128<byte> upperShuffleMask = upperShuffleMask_CopyToBoolArray;