Remove spurious assertion check causing .NET Core crashes (#89986)

* Remove spurious assertion check causing .NET Core crashes
Co-authored-by: NAaron Robinson <arobins@microsoft.com>
Co-authored-by: NJan Kotas <jkotas@microsoft.com>

src/libraries/System.Private.CoreLib/src/System/Text/Ascii.Utility.cs

@@ -2146,7 +2146,8 @@ private static unsafe nuint NarrowUtf16ToAscii_Intrinsified_256(char* pUtf16Buff
             // jumps as much as possible in the optimistic case of "all ASCII". If we see non-ASCII
             // data, we jump out of the hot paths to targets at the end of the method.
 
-            Debug.Assert(Vector256.IsHardwareAccelerated, "Vector256 is required.");
+            // Commented out to workaround https://github.com/dotnet/runtime/issues/90265
+            // Debug.Assert(Vector256.IsHardwareAccelerated, "Vector256 is required.");
             Debug.Assert(BitConverter.IsLittleEndian, "This implementation assumes little-endian.");
             Debug.Assert(elementCount >= 2 * Vector256.Size);