Remove stray " character from docstring (#3852)

src/instance.rs

@@ -766,7 +766,7 @@ impl<T> IntoPy<PyObject> for Borrowed<'_, '_, T> {
 /// # A note on `Send` and `Sync`
 ///
 /// Accessing this object is threadsafe, since any access to its API requires a [`Python<'py>`](crate::Python) token.
-/// As you can only get this by acquiring the GIL, `Py<...>` "implements [`Send`] and [`Sync`].
+/// As you can only get this by acquiring the GIL, `Py<...>` implements [`Send`] and [`Sync`].
 ///
 /// [`Rc`]: std::rc::Rc
 /// [`RefCell`]: std::cell::RefCell