Simplify discard call sites: inline single-use bool vars, remove redundant comments

Agent-Logs-Url: https://github.com/dadhi/FastExpressionCompiler/sessions/efa537b8-0c0e-4172-9ba3-1401feacbf6a

Co-authored-by: dadhi <39516+dadhi@users.noreply.github.com>

Author: Copilot

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -10938,8 +10938,7 @@ private static StringBuilder ToCSharpBlock(this Expression expr, StringBuilder s
             else
             {
                 sb.NewLineIndent(lineIndent + indentSpaces);
-                var needsDiscard = expr != null && expr.NeedsDiscardWhenUsedAsStatement();
-                if (needsDiscard) // it requires some assignment target to avoid error or warning
+                if (expr != null && expr.NeedsDiscardWhenUsedAsStatement())
                     sb.Append("_ = ");
                 sb = expr?.ToCSharpString(sb, EnclosedIn.ParensByDefault, ref ctx,
                     lineIndent + indentSpaces, stripNamespace, printType, indentSpaces, notRecognizedToCode) ?? sb.Append("null");
@@ -11164,7 +11163,7 @@ private static StringBuilder BlockToCSharpString(this BlockExpression b, StringB
                     sb.NewLineIndent(lineIndent);
                     var nodeType = expr.NodeType;
                     var returningCondOrCoalesceOrCall = expr.NeedsDiscardWhenUsedAsStatement();
-                    if (returningCondOrCoalesceOrCall) // it requires some assignment target to avoid error or warning
+                    if (returningCondOrCoalesceOrCall)
                         sb.Append("_ = ");
 
                     expr.ToCSharpString(sb, EnclosedIn.Block, ref ctx,