Always output CASE expression alias in EXPLAIN output

Remove the condition that skipped quoted aliases in CASE expressions.
ClickHouse EXPLAIN AST shows the alias regardless of whether it was
quoted in the original SQL.

Fixes test: 02244_casewithexpression_return_type/stmt1

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

internal/explain/functions.go

@@ -1536,12 +1536,7 @@ func explainIsNullExpr(sb *strings.Builder, n *ast.IsNullExpr, indent string, de
 }
 
 func explainCaseExpr(sb *strings.Builder, n *ast.CaseExpr, indent string, depth int) {
-	// Only output alias if it's unquoted (ClickHouse doesn't show quoted aliases)
-	alias := ""
-	if n.Alias != "" && !n.QuotedAlias {
-		alias = n.Alias
-	}
-	explainCaseExprWithAlias(sb, n, alias, indent, depth)
+	explainCaseExprWithAlias(sb, n, n.Alias, indent, depth)
 }
 
 func explainCaseExprWithAlias(sb *strings.Builder, n *ast.CaseExpr, alias string, indent string, depth int) {

parser/testdata/02244_casewithexpression_return_type/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true
-  }
-}
+{}