doc: fix FilterRole and RegExpRole doc

proxyroles/filterrole.cpp

@@ -12,6 +12,7 @@ namespace qqsfpm {
     A FilterRole is a \l ProxyRole that returns \c true for rows matching all its filters.
 
     In the following example, the \c isAdult role will be equal to \c true if the \c age role is superior or equal to 18.
+    \code
     SortFilterProxyModel {
         sourceModel: personModel
         proxyRoles: FilterRole {

proxyroles/regexprole.cpp

@@ -13,6 +13,7 @@ namespace qqsfpm {
     A RegExpRole is a \l ProxyRole that provides a role for each named capture group of its regular expression \l pattern.
 
     In the following example, the \c date role of the source model will be extracted in 3 roles in the proxy moodel: \c year, \c month and \c day.
+    \code
     SortFilterProxyModel {
         sourceModel: eventModel
         proxyRoles: RegExpRole {