fix(ts/fast-dts): Emit readonly for Object getter prop (#10492)

**Related issue:**

- Closes #10491

Author: magic-akari

.changeset/fair-ghosts-glow.md

@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc_typescript: patch
+---
+
+fix(typescript/dts): Emit `readonly` for Object getter prop

crates/swc_typescript/src/fast_dts/types.rs

@@ -196,7 +196,7 @@ impl FastDts {
                         let (key, computed) = self.transform_property_name_to_expr(&getter.key);
                         members.push(TsTypeElement::TsPropertySignature(TsPropertySignature {
                             span: DUMMY_SP,
-                            readonly: is_const,
+                            readonly: true,
                             key: Box::new(key),
                             computed,
                             optional: false,

crates/swc_typescript/tests/fixture/symbol-properties.snap

@@ -5,7 +5,7 @@ export declare const foo: {
     [Symbol.iterator]: () => void;
     [Symbol.asyncIterator]: () => Promise<void>;
     [globalThis.Symbol.iterator]: () => void;
-    [Symbol.toStringTag]: string;
+    readonly [Symbol.toStringTag]: string;
 };
 export declare abstract class Foo {
     [Symbol.iterator](): void;