fix(evince): remove empty extglob alternation segment

Introduced by yours truly.

scop#751 (comment)

Author: scop

completions/evince

@@ -25,7 +25,7 @@ _evince()
         return
     fi
 
-    _filedir '@(@(?(e)ps|?(E)PS|[pf]df|[PF]DF|dvi|DVI)?(.gz|.GZ|.bz2|.BZ2|.xz|.XZ)|cb[7rtz]|djv?(u)|tif?(f)||?(o)xps)'
+    _filedir '@(@(?(e)ps|?(E)PS|[pf]df|[PF]DF|dvi|DVI)?(.gz|.GZ|.bz2|.BZ2|.xz|.XZ)|cb[7rtz]|djv?(u)|tif?(f)|?(o)xps)'
 } &&
     complete -F _evince evince