Minor typos in groff_font(5) man page

[Jim Avera]

Some gobble got into the groff_font(5) man page.  Unsensible bits are hightlighted:

"The  depth subfield gives the depth of the glyph, that is, the
distance below the lowest point below the  baseline
to which the glyph extends (downwards is positive);
if a glyph does not extend below above the baseline, it  should  be..."

Betcha nobody reads that very often.

-Jim