run/locale.t: silence shell warnings

A couple of tests do

    local $ENV{LC_ALL} = "invalid";
    fresh_perl_is(...);

this causes a shell to be invoked with an invalid locale. Some shells
such as bash, become very noisy in this case:

    $ LC_ALL=invalid /bin/sh -c 'echo yes'
    /bin/sh: warning: setlocale: LC_ALL: cannot change locale (invalid): No such file or directory
    yes
    $

Silence these warnings by temporarily closing STDERR. Since the
fresh_perl_is() scripts themselves are run with STDERR set to /dev/null
anyway, this isn't a hardship.
run/locale.t: reindent block

Re-indent a block of code after the previous commit added an extra scope.
Whitespace-only change