Fix pedantic designated initializers warning
Short version: fix pedantic warnings by setting C++20
Long version:
In recurrenceperiodmodel.cpp
designated initializers are used. When
compiling with -Wpedantic
The errors like the following are printed:
../src/recurrenceperiodmodel.cpp: In member function ‘void ReccurencePeriodModel::initialize()’:
../src/recurrenceperiodmodel.cpp:25:10: warning: C++ designated initializers only available with ‘-std=c++2a’ or ‘-std=gnu++2a’ [-Wpedantic]
25 | {.periodType = Recurrence::rNone, .periodTypeDesc = periodDecription(Recurrence::rNone)},
| ^
To fix this set the required C++ version to C++20.