Remove Browser implementation of PBKDF2 one-shot

It's the same thing as the managed implementation now

src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj

@@ -576,7 +576,7 @@
     <Compile Include="System\Security\Cryptography\OidLookup.NoFallback.cs" />
     <Compile Include="System\Security\Cryptography\OpenSsl.NotSupported.cs" />
     <Compile Include="System\Security\Cryptography\PasswordDeriveBytes.NotSupported.cs" />
-    <Compile Include="System\Security\Cryptography\Pbkdf2Implementation.Browser.cs" />
+    <Compile Include="System\Security\Cryptography\Pbkdf2Implementation.Managed.cs" />
     <Compile Include="System\Security\Cryptography\RandomNumberGeneratorImplementation.Browser.cs" />
     <Compile Include="System\Security\Cryptography\RC2CryptoServiceProvider.NotSupported.cs" />
     <Compile Include="System\Security\Cryptography\RC2Implementation.NotSupported.cs" />

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/Pbkdf2Implementation.Browser.cs

-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-using System.Diagnostics;
-using Internal.Cryptography;
-
-namespace System.Security.Cryptography
-{
-    internal static partial class Pbkdf2Implementation
-    {
-        public static void Fill(
-            ReadOnlySpan<byte> password,
-            ReadOnlySpan<byte> salt,
-            int iterations,
-            HashAlgorithmName hashAlgorithmName,
-            Span<byte> destination)
-        {
-            Debug.Assert(!destination.IsEmpty);
-            Debug.Assert(hashAlgorithmName.Name is not null);
-
-            FillManaged(password, salt, iterations, hashAlgorithmName, destination);
-        }
-
-        private static void FillManaged(
-            ReadOnlySpan<byte> password,
-            ReadOnlySpan<byte> salt,
-            int iterations,
-            HashAlgorithmName hashAlgorithmName,
-            Span<byte> destination)
-        {
-            using (Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(
-                password,
-                salt,
-                iterations,
-                hashAlgorithmName))
-            {
-                deriveBytes.GetBytes(destination);
-            }
-        }
-    }
-}