modport declarations should start on own line about verible

[fangism]

b/144618226

[fangism]

Debugging verilog_format --show_token_partition_tree reveals:

Full token partition tree:
{ ([<auto>]) @{}
  { ([<auto>]) @{0}
    { ([interface foo_if ;]) }
  }
  { (  [<auto>]) @{1}
    { (  [modport tb ( output a , b , input c , d ) ; modport dut ( output a , b , input c , d ) ;]) }
  }
  { ([endinterface]) }
}

Clearly just needs a partition cut point.