use filesystem instead of experimental

Use filesystem now that it should be available instead of
experimental::filesystem.

Change-Id: Ia9b17f33ced70fe2f1f12f11d8708d15ff422bfa
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/fs.cpp b/fs.cpp
index 0c20d83..244fb8b 100644
--- a/fs.cpp
+++ b/fs.cpp
@@ -16,13 +16,13 @@
 
 #include "fs.hpp"
 
-#include <experimental/filesystem>
+#include <filesystem>
 #include <string>
 #include <vector>
 
 namespace blobs
 {
-namespace fs = std::experimental::filesystem;
+namespace fs = std::filesystem;
 
 std::vector<std::string> getLibraryList(const std::string& path,
                                         PathMatcher check)