access-mocsy: remove version gtracers and update README

[harshula]

1. Test CI with this change
2. It doesn't look like version gtracers is still used: https://github.com/search?q=org%3AACCESS-NRI+gtracers&type=code

[harshula]

The workaround is to depend on CMake. However, that does not address the root cause of this problem, which appears to be related to the concretization:

https://github.com/ACCESS-NRI/access-spack-packages/actions/runs/22930104845/job/66561489922#step:20:33

 ==> Concretized 1 spec:
 -   awfffmf  access-mocsy@stable build_system=makefile commit=b136e1a70b9959333b0258b07863ebb05c4ff5f7 platform=linux os=rocky8 target=x86_64 %c,fortran=gcc@13.2.0

For example, the MOM5 SPR has a similar pattern, but it is able to concretize as expected to use CMake with gcc:

==> Concretized 1 spec:
 -   5572z5m  mom5@access-om2~deterministic~ipo build_system=cmake build_type=RelWithDebInfo commit=995fe497e1b91342f465cbed66eaa1336f183ec0 generator=make platform=linux os=rocky8 target=x86_64 %c,fortran=gcc@13.2.0

[harshula]

Experiments

    #build_system(conditional("cmake", when="@2025.07.000:"), "makefile", default="cmake")
    build_system("cmake", "makefile", default="cmake")

 -   access-mocsy@stable build_system=makefile commit=b136e1a70b9959333b0258b07863ebb05c4ff5f7 platform=linux os=rocky8 target=x86_64 %c,fortran=gcc@13.2.0

    depends_on("c", type="build")
    depends_on("cxx", type="build")
    depends_on("fortran", type="build")
    depends_on("mpi")

    #build_system(conditional("cmake", when="@2025.07.000:"), "makefile", default="cmake")
    build_system("cmake", "makefile", default="cmake")

 -   access-mocsy@stable build_system=makefile commit=b136e1a70b9959333b0258b07863ebb05c4ff5f7 platform=linux os=rocky8 target=x86_64 %c,cxx,fortran=gcc@13.2.0

    depends_on("c", type="build")
    depends_on("fortran", type="build")
    depends_on("cmake", type="build")
    depends_on("mpi")

    #build_system(conditional("cmake", when="@2025.07.000:"), "makefile", default="cmake")
    build_system("cmake", "makefile", default="cmake")

 -   access-mocsy@stable~ipo~shared build_system=cmake build_type=RelWithDebInfo commit=b136e1a70b9959333b0258b07863ebb05c4ff5f7 generator=make precision=2 platform=linux os=rocky8 target=x86_64 %c,fortran=gcc@13.2.0

[harshula]

The original reason for opening this PR is fixed in PR ACCESS-NRI/spack-config#107

[aidanheerdegen]

README seems fine to me.

The package changes I'll leave it to @dougiesquire to approve.

[dougiesquire]

Thanks @harshula - LGTM