Simplify using auto return type

dune/contact/assemblers/nbodyassembler.hh

@@ -132,12 +132,12 @@ public:
     static void concatenateVectors(const VectorTypeContainer& parts, VectorType& whole);
 
     /** \brief Get the contact couplings. */
-    const std::vector<std::shared_ptr<CouplingType> >& getContactCouplings() const {
+    const auto& getContactCouplings() const {
         return contactCoupling_;
     }
 
     /** \brief Get the contact couplings. */
-    std::vector<std::shared_ptr<CouplingType> >& getContactCouplings() {
+    auto& getContactCouplings() {
         return contactCoupling_;
     }
 
@@ -164,7 +164,7 @@ public:
     }
 
     /** \brief Get reference to i'th coupling. */
-    const CouplingPair<GridType, GridType, field_type>& getCoupling(size_t i) const {return coupling_[i];}
+    const auto& getCoupling(size_t i) const {return coupling_[i];}
 
 protected:
     /** \brief Compute the transposed mortar transformation matrix. */