fix broken link in docs (#4940)

Author: ngoldbaum

guide/src/conversions/traits.md

@@ -532,7 +532,7 @@ struct RustyStruct {
 ```
 
 ### `IntoPyObject`
-The ['IntoPyObject'] trait defines the to-python conversion for a Rust type. All types in PyO3 implement this trait,
+The [`IntoPyObject`] trait defines the to-python conversion for a Rust type. All types in PyO3 implement this trait,
 as does a `#[pyclass]` which doesn't use `extends`.
 
 This trait defines a single method, `into_pyobject()`, which returns a [`Result`] with `Ok` and `Err` types depending on the input value. For convenience, there is a companion [`IntoPyObjectExt`] trait which adds methods such as `into_py_any()` which converts the `Ok` and `Err` types to commonly used types (in the case of `into_py_any()`, `Py<PyAny>` and `PyErr` respectively).