fix test pyop2 kernel compilation error with gcc14

[qbisi]

Description

Since gcc14, some -Wincompatible-pointer-types are treated as error,
especially when you define func (int a[2][3]) {...}
and pass func with a pointer int p[6].

This pr might not be the best solution, however, one should fix the op2 kernel code in tests/pyop2/test_vector_map.py. e.g.

    k = """
    static void k(int d[2], int vd[1][2]) {
    d[0] = vd[0][0];
    d[1] = vd[0][1];
    }"""

to

    k = """
    static void k(int d[2], int vd[2]) {
    d[0] = vd[0];
    d[1] = vd[1];
    }"""

at the cost of less human readability.

related issue: #4096

I am a nixpkgs commiter on the roadmap to build/test/package firedrake/petsc with the power of nix build system which claim a reproducible firedrake environment.

Glad to see the Modernization of the installation of firedrake and its component.