fix translation of about.rst into English

docs/source/about.rst

@@ -6,7 +6,7 @@ The iOpt is developed and maintained by the team from Nizhny Novgorod State Univ
 The results obtained by the supervising of prof. R.G. Strongin constitute a new direction in the field of models, methods and software tools for solving complex optimization problems (multi-extremal, multicriteria, with non-convex constraints, mixed-integer, etc.).
 
 The main books
-==============
+--------------
 
 1. Strongin R.G., Gergel V.P., Grishagin V.A., Barkalov K.A. Parallel computing in global optimization problems // MSU Press, 2013. [in Russian] (https://msupress.com/catalogue/books/book/parallelnye-vychisleniya-v-zadachakh-globalnoy-optimizatsii/).
 2. Strongin R.G., Sergeyev Y.D. Global Optimization with Non-Convex Constraints // Springer New York, NY, 2000. (https://link.springer.com/book/10.1007/978-1-4615-4677-1).