doc: fix a broken link in fs.md

PR-URL: #31373
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/api/fs.md

@@ -5574,4 +5574,4 @@ the file contents.
 [chcp]: https://ss64.com/nt/chcp.html
 [inode]: https://en.wikipedia.org/wiki/Inode
 [support of file system `flags`]: #fs_file_system_flags
-[Writable Stream]: #stream_class_stream_writable
+[Writable Stream]: stream.html#stream_class_stream_writable