I used patch from this issue https://drupal.org/node/1665164 for this problem.
simple provide the block tilte at the the of block configuration ........... that will override this title..
To change the title of the block provided by the Facet API, go to admin/structure/block and choose the block of which you want to chage the title. Click on the
Configure link and then change the title of block from Block Title textfield.