Remove issue-557 char-default tests that depend on a fix not in this branch

Tests TestCharDefaultValueForStringParameterAsync and TestCharLiteralDefaultValueForStringParameterAsync
require the FixCharDefaultsForStringParams fix which is in a separate PR. Removing them from
the issue-827 branch to prevent test failures.

https://claude.ai/code/session_01AkwUvu3XuCdj3D4axoX4UX

Author: claude

Tests/CSharp/MemberTests/MemberTests.cs

@@ -1576,49 +1576,4 @@ private void OptionalByRefWithDefault([Optional][DefaultParameterValue(""a"")] r
 CS7036: There is no argument given that corresponds to the required parameter 'str1' of 'MissingByRefArgumentWithNoExplicitDefaultValue.ByRefNoDefault(ref string)'
 ");
     }
-
-    [Fact]
-    public async Task TestCharDefaultValueForStringParameterAsync()
-    {
-        // Issue #557: VB allows Char as a default value for a String parameter, but C# does not.
-        // The fix replaces the default with null and prepends a null-coalescing assignment in the body.
-        await TestConversionVisualBasicToCSharpAsync(
-            @"Module TestModule
-    Friend Const DlM As Char = ""^""c
-
-    Friend Function LeftSideOf(Optional ByVal strDlM As String = DlM) As String
-        Return strDlM
-    End Function
-End Module", @"
-internal static partial class TestModule
-{
-    internal const char DlM = '^';
-
-    internal static string LeftSideOf(string strDlM = null)
-    {
-        strDlM = strDlM ?? DlM.ToString();
-        return strDlM;
-    }
-}");
-    }
-
-    [Fact]
-    public async Task TestCharLiteralDefaultValueForStringParameterAsync()
-    {
-        // Issue #557: inline char literal as default value for a String parameter.
-        await TestConversionVisualBasicToCSharpAsync(
-            @"Class TestClass
-    Friend Function Foo(Optional s As String = ""^""c) As String
-        Return s
-    End Function
-End Class", @"
-internal partial class TestClass
-{
-    internal string Foo(string s = null)
-    {
-        s = s ?? '^'.ToString();
-        return s;
-    }
-}");
-    }
 }