Update Glade.pod

remove apostrophe from plurals used as words [1], e.g. s/ASF's/ASFs/ — understandably arguable, but reads better e.g. in Marpa's ASF's vs. Marps's ASFs

[1] DO NOT use an apostrophe to form the plural of capital letters used as words, abbreviations that contain no interior periods, and numerals used as nouns:
the three Rs.
the 1990s
lengthy URLs
— http://www.dailywritingtips.com/when-to-form-a-plural-with-an-apostrophe/