Removed redundant cast to c_str() in ConfigMgr::Reload function.

cppcheck performance warning:
[src/server/shared/Configuration/Config.cpp:62]: (performance) Passing the
result of c_str() to a function that takes std::string as argument no. 1 is
slow and redundant.
Merge pull request #13060 from LogvinovLeon/master

Removed redundant cast to c_str() in ConfigMgr::Reload function.