Replace std::experimental::filesystem with std::filesystem

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I91d2f1b7a8858ba8c676b68693863bb35b56dffc
diff --git a/powercap.cpp b/powercap.cpp
index ccf2998..26c1ee7 100644
--- a/powercap.cpp
+++ b/powercap.cpp
@@ -22,7 +22,7 @@
 constexpr auto POWER_CAP_ENABLE_PROP = "PowerCapEnable";
 
 using namespace phosphor::logging;
-namespace fs = std::experimental::filesystem;
+namespace fs = std::filesystem;
 
 uint32_t PowerCap::getOccInput(uint32_t pcap, bool pcapEnabled)
 {