boost::property_tree::write_json always pretty prints ] when encoding arrays

[fisher]

generally the result is unnecessary white space in the resulting json string

this can be resolved by changing line 96 of 'boost\property_tree\detail\json_parser_write.hpp' from

            stream << Str(4 * indent, Ch(' ')) << Ch(']');

to

            if (pretty) stream << Str(4 * indent, Ch(' '));
            stream << Ch(']');

which is consistent in style and functionality with lines 120 and 121 of the same file

[Sebastian Redl]

Dupe of #7180.