Updating doctest tag

[eHonnef]

There is a issue with the current doclib tag and the glibc-2.34, as mentioned here.

I updated the Doctest to the latest tag.

Before updating:

./build/_deps/doctest-src/doctest/doctest.h:4036:47: error: size of array ‘altStackMem’ is not an integral constant-expression
 4036 |         static char             altStackMem[4 * SIGSTKSZ];
      |                                               ^
make[2]: *** [CMakeFiles/main.dir/build.make:76: CMakeFiles/main.dir/app/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:930: CMakeFiles/main.dir/all] Error 2
make: *** [Makefile:146: all] Error 2

After updating:

Consolidate compiler generated dependencies of target engine
[ 16%] Building CXX object CMakeFiles/engine.dir/src/example.cpp.o
[ 16%] Built target engine
Consolidate compiler generated dependencies of target main
[ 33%] Building CXX object CMakeFiles/main.dir/app/main.cpp.o
[ 50%] Linking CXX executable main
[ 50%] Built target main
[ 66%] Building CXX object tests/CMakeFiles/unit_tests.dir/main.cpp.o
[ 83%] Building CXX object tests/CMakeFiles/unit_tests.dir/dummy.cpp.o
[100%] Linking CXX executable ../unit_tests
[100%] Built target unit_tests