Un-deprecate RBParameters::get_parameter_names()

Now that we have the possibility of multi-step RBParameters objects,
the advice given in the previous deprecation message is no longer
accurate, since it is not efficient to iterate over hundreds (or
possibly thousands) of steps just to get the list of parameter names.

Author: jwpeterson

include/reduced_basis/rb_parameters.h

@@ -284,22 +284,20 @@ class RBParameters
   /**
    * Fill \p param_names with the names of the parameters.
    *
-   * \deprecated to avoid making it too easy to create copies that in
-   * most circumstances aren't needed.  If you really need a list of
-   * the parameter names, the best approach is to iterate over this
-   * object using the begin()/end() APIs and build a std::set that
-   * way.
+   * Note: this function was previously deprecated, but now that
+   * multi-step RBParameters objects are possible, this is actually
+   * the most efficient way to get a list of the parameter names
+   * stored on this object.
    */
   void get_parameter_names(std::set<std::string> & param_names) const;
 
   /**
    * Fill \p param_names with the names of the extra parameters.
    *
-   * \deprecated to avoid making it too easy to create copies that in
-   * most circumstances aren't needed.  If you really need a list of
-   * the parameter names, the best approach is to iterate over this
-   * object using the extra_begin()/extra_end() APIs and build a std::set that
-   * way.
+   * Note: this function was previously deprecated, but now that
+   * multi-step RBParameters objects are possible, this is actually
+   * the most efficient way to get a list of the parameter names
+   * stored on this object.
    */
   void get_extra_parameter_names(std::set<std::string> & param_names) const;
 

src/reduced_basis/rb_parameters.C

@@ -192,17 +192,13 @@ unsigned int RBParameters::n_steps() const
 
 void RBParameters::get_parameter_names(std::set<std::string> & param_names) const
 {
-  libmesh_deprecated();
-
   param_names.clear();
   for (const auto & pr : _parameters)
     param_names.insert(pr.first);
 }
 
 void RBParameters::get_extra_parameter_names(std::set<std::string> & param_names) const
 {
-  libmesh_deprecated();
-
   param_names.clear();
   for (const auto & pr : _extra_parameters)
     param_names.insert(pr.first);