Make typedefs brief

include/libsemigroups/types.hpp

@@ -38,8 +38,6 @@ namespace libsemigroups {
   //!
   //! This file contains functionality for various types used in
   //! ``libsemigroups``.
-
-  //! \ingroup types_group
   //!
   //! @{
 
@@ -90,13 +88,13 @@ namespace libsemigroups {
                            std::conditional_t<N >= 0x100, uint16_t, uint8_t>>>;
   };
 
-  //! Type for the index of a generator of a semigroup.
+  //! \brief Type for the index of a generator of a semigroup.
   using letter_type = size_t;
 
-  //! Type for a word over the generators of a semigroup.
+  //! \brief Type for a word over the generators of a semigroup.
   using word_type = std::vector<letter_type>;
 
-  //! Type for a pair of word_type (a *relation*) of a semigroup.
+  //! \brief Type for a pair of word_type (a *relation*) of a semigroup.
   using relation_type = std::pair<word_type, word_type>;
 
   //! @}