Update Changelog.md

Co-authored-by: Ronny Bergmann <git@ronnybergmann.net>

Author: hajg-ijk

Changelog.md

@@ -51,7 +51,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * a `gradient=` keyword in several `Stepsize`s, such that one can avoid to internally avoid computing the gradient again.
 * used the ``gradient=` keyword in
   * `alternating_gradient_descent`
-  * conjugate_gradient
+  * `conjugate_gradient`
   * `Frank_Wolfe_method`
   * `gradient_descent`
   * `interior_point_newton`