chore(docs): fix docs for writer_options

[meteorgan]

Which issue does this PR close?

None

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

AI Usage Statement

[Xuanwo]

doc test failed:

---- core/src/types/operator/operator.rs - types::operator::operator::Operator::writer_options (line 923) stdout ----
error[E0433]: failed to resolve: use of unresolved module or unlinked crate `options`
  --> core/src/types/operator/operator.rs:933:9
   |
13 |         options::WriteOptions {
   |         ^^^^^^^ use of unresolved module or unlinked crate `options`
   |
   = help: if you wanted to use a crate named `options`, use `cargo add options` to add it to your `Cargo.toml`
help: an enum with a similar name exists
   |
13 -         options::WriteOptions {
13 +         Option::WriteOptions {
   |
help: consider importing this module
   |
 2 + use opendal_core::options;
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0433`.
Couldn't compile the test.

failures:
    core/src/types/operator/operator.rs - types::operator::operator::Operator::writer_options (line 923)