Remove references to experimental filesystem

We're at CPP17 everywhere now, no need to keep the
experimental refrerence.

Tested: It builds

Change-Id: I5f6571eb411bf055e9715f7d96d1be5a3cb2e119
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/include/webassets.hpp b/include/webassets.hpp
index 9bd40db..daead98 100644
--- a/include/webassets.hpp
+++ b/include/webassets.hpp
@@ -1,7 +1,5 @@
 #pragma once
 
-#include "filesystem.hpp"
-
 #include <crow/app.h>
 #include <crow/http_request.h>
 #include <crow/http_response.h>
@@ -9,6 +7,7 @@
 
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/container/flat_set.hpp>
+#include <filesystem>
 #include <fstream>
 #include <string>