haikudepot: Fix 'new[]' array freed with 'delete'

buffer is allocated by new[] in _UnpackCaptcha(), but freed by delete.
Pointed out by LGTM.

Change-Id: I6feee3f9791950c33bbc2037c7809e21f250fa47
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2226
Reviewed-by: Jérôme Duval <[email protected]>

src/apps/haikudepot/ui/UserLoginWindow.cpp

@@ -875,7 +875,7 @@ UserLoginWindow::_UnpackCaptcha(BMessage& responsePayload, Captcha& captcha)
 			captcha.SetToken(token);
 			captcha.SetPngImageData(buffer, decodedSize);
 		}
-		delete buffer;
+		delete[] buffer;
 	}
 
 	return result;