gnu: guile-static: Add missing hunk in guile-default-utf8.patch.

Before that, the ‘guile’ binary from ‘guile-static-stripped’ would abort
as it tries and fails to open an iconv descriptor for ISO-8859-1.

* gnu/packages/patches/guile-default-utf8.patch: Add missing hunk for
  Guile 2.0.9.