[stuff-leftovers] add another missing storageprovider ctor

dune/xt/common/memory.hh

@@ -285,6 +285,11 @@ public:
   {
   }
 
+  explicit ConstStorageProvider(std::shared_ptr<T> tt)
+    : storage_(Common::make_unique<internal::ConstAccessByPointer<T>>(tt))
+  {
+  }
+
   explicit ConstStorageProvider(std::unique_ptr<const T>&& tt)
     : storage_(tt)
   {