Modify the "Modules used, but not reported" section *in place* in the report

Because the test code was removing the "Modules used, but not reported"
section and then putting it back at the end with the missing sitecustomize,
the section ended up swaped with the "Possible proxies" one.

This is what happens otherwise:

    http://www.cpantesters.org/cpan/report/d20bc1a9-77c8-1014-b56a-db2593e8ee67

    #   Failed test 'Trace for: perl -d:TraceUse -MM4 -MM1 -e M5->load'
    #   at t\traceuse.t line 335.
    #     Structures begin differing at:
    #          $got->[8] = 'Modules used, but not reported:'
    #     $expected->[8] = 'Possible proxies:'
    # --- Got ---
    # Modules used from -e:
    #    1.  M4, -e line 0 [main]
    #    2.    M5, M4.pm line 3
    #    3.      M6, M5.pm line 9 [M5::in]
    #    7.      M7 0, M5.pm line 4
    #    4.  M1, -e line 0 [main]
    #    5.    M2, M1.pm line 3
    #    6.      M3, M2.pm line 3
    # Modules used, but not reported:
    #   c:/Perl1664/site/lib/sitecustomize.pl
    # Possible proxies:
    #    2 -e line 0, sub main::BEGIN
    # --- Expected ---
    # Modules used from -e:
    #    1.  M4, -e line 0 [main]
    #    2.    M5, M4.pm line 3
    #    3.      M6, M5.pm line 9 [M5::in]
    #    7.      M7 0, M5.pm line 4
    #    4.  M1, -e line 0 [main]
    #    5.    M2, M1.pm line 3
    #    6.      M3, M2.pm line 3
    # Possible proxies:
    #    2 -e line 0, sub main::BEGIN
    # Modules used, but not reported:
    #   c:/Perl1664/site/lib/sitecustomize.pl