docs: rust: update Rust docs output path

The Rust code documentation output path moved from `rust/doc` to
`Documentation/output/rust/rustdoc`, thus update the old reference.

Fixes: 48fadf4400 ("docs: Move rustdoc output, cross-reference it")
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20231018160145.1017340-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Documentation/rust/general-information.rst

@@ -29,7 +29,7 @@ target with the same invocation used for compilation, e.g.::
 
 To read the docs locally in your web browser, run e.g.::
 
-	xdg-open rust/doc/kernel/index.html
+	xdg-open Documentation/output/rust/rustdoc/kernel/index.html
 
 To learn about how to write the documentation, please see coding-guidelines.rst.