[jest-editor-support] update definition (#6212)

According to (the implementation)[https://github.com/facebook/jest/blob/f4f51914d577dc53748f599f3f626dfe3154883e/packages/jest-editor-support/src/Snapshot.js#L106] the first parameter of Snapshot constructor is optional.

Author: stephtr

packages/jest-editor-support/index.d.ts

@@ -179,6 +179,6 @@ export interface SnapshotMetadata {
 }
 
 export class Snapshot {
-  constructor(parser: any, customMatchers?: string[]);
+  constructor(parser?: any, customMatchers?: string[]);
   getMetadata(filepath: string): SnapshotMetadata[];
 }