doc: printf: make "java" encoding example more standard

doc: printf: make "java" encoding example more standard

Note using iconv(1) rather than recode(1) is not appropriate
for this example, as the required functionality is only
available on libiconv's iconv implementation, which is
not installed on most systems.

* doc/coreutils.texi (printf invocation): Use env rather than
/usr/local/bin for the printf command.  Escape '%' so more robust.
Also use a locale that exists on modern systems.