Fix max allowed arguments

It should be 4 as we have a total of four arguments including the <input>

I was getting the following error on running the script:

```
$ ./parquet-tools dump -c label ../part-m-00000.gz.parquet
dump -c label ../part-m-00000.gz.parquet
Invalid arguments: missing required arguments

usage: parquet-dump [option...] <input>
where option is one of:
    -c,--column <arg>  Dump only the given column, can be specified more than
                       once
    -d,--disable-data  Do not dump column data
       --debug         Disable color output even if supported
    -h,--help          Show this help string
    -m,--disable-meta  Do not dump row group and page metadata
       --no-color      Disable color output even if supported
where <input> is the parquet file to print to stdout
```