op_dump() - remove extra indentation from PMOP

op_dump() - remove extra indentation from PMOP

When dumping a PMOP, it displays the PMOP-specific fields with
an extra set of braces and level of indentation, e.g.

    {
        TYPE = match  ===> 1
        FLAGS = (VOID,SLABBED)
        PRIVATE = (RTIME)
        {
            PMf_PRE /abc/ (RUNTIME)
            PMFLAGS = (SCANFIRST,ALL)
        }
    }

This is visually confusing, because child ops are shown in the same way.
This commit removes the extra indentation:

    {
        TYPE = match  ===> 1
        FLAGS = (VOID,SLABBED)
        PRIVATE = (RTIME)
        PMf_PRE /abc/ (RUNTIME)
        PMFLAGS = (SCANFIRST,ALL)
    }