www/joomla3: update to 3.8.11.

Joomla 3.8.11 addresses several bugs and improvements, including:

Fix for the Missing "Select Type" field in the Extensions Manager #20881
Replace the URL parameter "limitstart=0" by "start=0" when SEF is enabled #19452
Remove non callable array items from field categories #20093
Articles - Category Module: New showon attribute for form fields #20950
Fix OpenSearch implementation #20937
Fix for tag filtering in Featured Articles view in administrator #21138
Fix for filtering Featured Articles by access level in administrator #21168
Media manager: relative paths for video files #21156
Com_menus: removal of useglobal attribute #21095
Multilingual Associations Component: fix associations in sidebyside view for contact and newsfeeds #21180