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.

doc/coreutils.texi

@@ -13255,10 +13255,10 @@ is how to convert a piece of text into a shell script which will output
 this text in a locale-independent way:
 
 @example
-$ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \
+$ LC_CTYPE=zh_TW.big5 env printf \
     '\u4e2d\u6587\n' > sample.txt
 $ recode BIG5..JAVA < sample.txt \
-    | sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \
+    | sed -e "s|^|env printf '|" -e "s|%|%%|g" -e "s|$|\\\\n'|" \
     > sample.sh
 @end example