[clang-repl] [test] Make an XFAIL more precise (#70991)

The const.cpp testcase fails when running in MSVC mode, while it does
succeed in MinGW mode.

In MSVC mode, there are more constructor invocations than expected, as
the printout looks like this:

    A(1), this = 0000025597930000
    A(1), this = 0000025597930000
    f: this = 0000025597930000, val = 1
    A(1), this = 0000025597930000
    f: this = 0000025597930000, val = 1
    ~A, this = 0000025597930000, val = 1
    ~A, this = 0000025597930000, val = 1
    ~A, this = 0000025597930000, val = 1

While the expected printout looks like this:

    A(1), this = 000002C903E10000
    f: this = 000002C903E10000, val = 1
    f: this = 000002C903E10000, val = 1
    ~A, this = 000002C903E10000, val = 1