chore: fix eslint in blocksuite (#9232)

blocksuite/blocks/src/attachment-block/attachment-service.ts

@@ -26,7 +26,7 @@ import { addSiblingAttachmentBlocks } from './utils.js';
 export class AttachmentBlockService extends BlockService {
   static override readonly flavour = AttachmentBlockSchema.model.flavour;
 
-  private _fileDropOptions: FileDropOptions = {
+  private readonly _fileDropOptions: FileDropOptions = {
     flavour: this.flavour,
     onDrop: async ({ files, targetModel, place, point }) => {
       if (!files.length) return false;

blocksuite/blocks/src/attachment-block/embed.ts

@@ -67,7 +67,7 @@ export class AttachmentEmbedService extends Extension {
     return this.configs.values();
   }
 
-  constructor(private configs: Map<string, AttachmentEmbedConfig>) {
+  constructor(private readonly configs: Map<string, AttachmentEmbedConfig>) {
     super();
   }