remove std::experimental usage

All of the std::experimental usages in this repository have a well
supported counterpart in std as of C++17.  Switch to use them.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4cdf5cd27053ce85c7f70c215ee9456f96f79f42
diff --git a/src/median.hpp b/src/median.hpp
index a3ffe67..8498726 100644
--- a/src/median.hpp
+++ b/src/median.hpp
@@ -59,12 +59,12 @@
         {
             const auto& storage = std::get<storageIndex>(item.second);
             // Don't count properties that don't exist.
-            if (std::get<valueIndex>(storage.get()).empty())
+            if (!std::get<valueIndex>(storage.get()).has_value())
             {
                 continue;
             }
             values.emplace_back(
-                any_ns::any_cast<T>(std::get<valueIndex>(storage.get())));
+                std::any_cast<T>(std::get<valueIndex>(storage.get())));
         }
 
         if (!values.empty())