refactor: remove extra default in max rows

[tshauck]

Which issue does this PR close?

Closes #.

Rationale for this change

Currently -h in the datafusion CLI shows the default for max rows twice.

What changes are included in this PR?

This PR removes the value from the argument help, so the default is only shown once.

Are these changes tested?

Yes, compiled and looked at the help.

currenly main shows:

        --maxrows <MAXROWS>
            The max number of rows to display for 'Table' format
            [default: 40] [possible values: numbers(0/10/...), inf(no limit)] [default: 40]

but after this PR, it'll show

        --maxrows <MAXROWS>
            The max number of rows to display for 'Table' format
            [possible values: numbers(0/10/...), inf(no limit)] [default: 40]

Note the how the 2nd one only has one [default: 40].

Are there any user-facing changes?

Minor, CLI help.

[jonahgao]

LGTM, thanks @tshauck