app: update/fix the About's authors.xsl.

Apply Jehans' fix to the authors.xsl to this branch as well. Adapt it to
consider "recent" as >= 2.8 and don't change the sorting.

app/dialogs/authors.xsl

@@ -11,8 +11,9 @@
   <xsl:template name="recent-contributor">
     <xsl:param name="role" />
     <xsl:apply-templates select="dc:contributor[contains(@role, $role) and
-                                 number(@last-active) >= 2             and
-                                 number(substring-after(@last-active, &quot;.&quot;)) >= 8]" />
+                                 ((number(@last-active) >= 2             and
+                                  number(substring-after(@last-active, &quot;.&quot;)) >= 8) or
+                                  number(@last-active) >= 3)]" />
   </xsl:template>
 
   <xsl:template match="/dc:gimp-authors">