doc: fix buffer api example code's token error

Buffer's Blob api example code has some token error

PR-URL: #40125
Reviewed-By: Qingyu Deng <i@ayase-lab.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/buffer.md

@@ -574,7 +574,7 @@ mc1.port2.postMessage(blob);
 mc2.port2.postMessage(blob);
 
 // The Blob is still usable after posting.
-data.text().then(console.log);
+blob.text().then(console.log);
 ```
 
 ```cjs
@@ -601,7 +601,7 @@ mc1.port2.postMessage(blob);
 mc2.port2.postMessage(blob);
 
 // The Blob is still usable after posting.
-data.text().then(console.log);
+blob.text().then(console.log);
 ```
 
 ## Class: `Buffer`