fix typo in class.md (PyO3#4901)

Author: lundybernard

guide/src/class.md

@@ -200,7 +200,7 @@ fn my_module(m: &Bound<'_, PyModule>) -> PyResult<()> {
 
 ## Bound<T> and interior mutability
 
-Often is useful to turn a `#[pyclass]` type `T` into a Python object and access it from Rust code. The [`Py<T>`] and [`Bound<'py, T>`] smart pointers are the ways to represent a Python object in PyO3's API. More detail can be found about them [in the Python objects](./types.md#pyo3s-smart-pointers) section of the guide.
+It is often useful to turn a `#[pyclass]` type `T` into a Python object and access it from Rust code. The [`Py<T>`] and [`Bound<'py, T>`] smart pointers are the ways to represent a Python object in PyO3's API. More detail can be found about them [in the Python objects](./types.md#pyo3s-smart-pointers) section of the guide.
 
 Most Python objects do not offer exclusive (`&mut`) access (see the [section on Python's memory model](./python-from-rust.md#pythons-memory-model)). However, Rust structs wrapped as Python objects (called `pyclass` types) often *do* need `&mut` access. Due to the GIL, PyO3 *can* guarantee exclusive access to them.