[Bug libstdc++/101234] Two tests require en_US.ISO-8859-15 but glibc no longer installs that by default.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101234

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Looks like the testsuite is incorrect, it should have been 'en_US.ISO8859-15'

I think that's exactly equivalent, the extra dash is optional.