Use std::map.contains as per latest c++

This commit replaces occurrences of 'find' with
'contains' to access elements in a std::map
according to the latest C++ standard (since C++20).

However, contains() is not suitable in all situations
as in the case where we want to use the element contained
in the map using contains(), then it would do 2 searches
instead of 1 in the case where we use find() which fetches
the element from the map also.

Here are some relevant links to C++ documentation and
resources:

[1]: https://en.cppreference.com/w/cpp/container/map/find
[2]: https://en.cppreference.com/w/cpp/container/map/contains
[3]: https://wg21.link/N4861

Signed-off-by: Sagar Srinivas <sagar.srinivas@ibm.com>
Change-Id: If589e52026417c1c14a6a946e48826b749034e9a
diff --git a/libpldmresponder/base.cpp b/libpldmresponder/base.cpp
index 8d7b918..e0708a4 100644
--- a/libpldmresponder/base.cpp
+++ b/libpldmresponder/base.cpp
@@ -111,7 +111,7 @@
 
     // DSP0240 has this as a bitfield8[N], where N = 0 to 31
     std::array<bitfield8_t, 32> cmds{};
-    if (capabilities.find(type) == capabilities.end())
+    if (!capabilities.contains(type))
     {
         return CmdHandler::ccOnlyResponse(request,
                                           PLDM_ERROR_INVALID_PLDM_TYPE);