fix(semantic): non-exported namespace member symbols flagged as exported

> Part of #4445

Fixes a bug where non-exported functions and variables inside of exported TS namespaces were being flagged with `SymbolFlags::Export`

```ts
export namespace Foo {
  // incorrectly flagged as exported
  function foo() { }
}
```

crates/oxc_semantic/src/builder.rs

@@ -1759,6 +1759,7 @@ impl<'a> SemanticBuilder<'a> {
                     .get_bindings(self.current_scope_id)
                     .get(module_declaration.id.name().as_str());
                 self.namespace_stack.push(*symbol_id.unwrap());
+                self.current_symbol_flags -= SymbolFlags::Export;
             }
             AstKind::TSTypeAliasDeclaration(type_alias_declaration) => {
                 type_alias_declaration.bind(self);

crates/oxc_semantic/tests/integration/modules.rs

@@ -186,6 +186,38 @@ fn test_exports_in_namespace() {
     test.has_some_symbol("bar").is_exported().test();
     let semantic = test.build();
     assert!(!semantic.module_record().exported_bindings.contains_key("bar"));
+
+    // namespace exported, member is not
+    let sources =
+        ["export namespace N { function foo() {} } ", "export namespace N { const foo = 1 } "];
+    for src in sources {
+        let test = SemanticTester::ts(src);
+        test.has_some_symbol("N").contains_flags(SymbolFlags::NameSpaceModule).is_exported().test();
+        test.has_some_symbol("foo").is_not_exported().test();
+    }
+
+    // namespace and member are both exported
+    let sources = [
+        "export namespace N { export function foo() {} } ",
+        "export namespace N { export const foo = 1 } ",
+    ];
+    for src in sources {
+        let test = SemanticTester::ts(src);
+        test.has_some_symbol("N").contains_flags(SymbolFlags::NameSpaceModule).is_exported().test();
+        test.has_some_symbol("foo").is_exported().test();
+    }
+
+    // namespace is not exported, but member is
+    let sources =
+        ["namespace N { export function foo() {} } ", "namespace N { export const foo = 1 } "];
+    for src in sources {
+        let test = SemanticTester::ts(src);
+        test.has_some_symbol("N")
+            .contains_flags(SymbolFlags::NameSpaceModule)
+            .is_not_exported()
+            .test();
+        test.has_some_symbol("foo").is_exported().test();
+    }
 }
 
 #[test]