Make writing wal header able to be sync

bindings/javascript/src/lib.rs

@@ -726,9 +726,12 @@ impl turso_core::DatabaseStorage for DatabaseFile {
     fn size(&self) -> turso_core::Result<u64> {
         self.file.size()
     }
-    fn truncate(&self, len: usize, c: Arc<turso_core::Completion>) -> turso_core::Result<()> {
-        let _ = self.file.truncate(len, c)?;
-        Ok(())
+    fn truncate(
+        &self,
+        len: usize,
+        c: turso_core::Completion,
+    ) -> turso_core::Result<turso_core::Completion> {
+        self.file.truncate(len, c)
     }
 }