[imp] Changing minimum upper limit search to 200 characters

See https://github.com/joomla/joomla-cms/issues/5103
To test in en-GB, add `var_dump ($upper_limit);` after line 33 `$upper_limit = $lang->getUpperLimitSearchWord();` in 
ROOT/modules/mod_search/mod_search.php

You should get `int 200`