Replace find method with contains method

- The intent behind of this commit is to replace the `find` method
  with the `contains` method.

- `contains` is a new feature of C++20, it will check if there is an
  element with key equivalent to key in the container and return
  true or false.

Tested: built ledManager repo successfully and CI passed.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I09121154983defe051c48e6470a976c5b229a2e7
diff --git a/serialize.cpp b/serialize.cpp
index c8f4e66..897b336 100644
--- a/serialize.cpp
+++ b/serialize.cpp
@@ -22,7 +22,7 @@
 
 bool Serialize::getGroupSavedState(const std::string& objPath) const
 {
-    return savedGroups.find(objPath) == savedGroups.end() ? false : true;
+    return savedGroups.contains(objPath);
 }
 
 void Serialize::storeGroups(const std::string& group, bool asserted)