Author: Amaia Anabitarte
MDL-77941 blocks_overview: Remove duplicated strings for zero states
http://git.moodle.org/gw?p=moodle.git;a=commit;h=f4a172afdeef89d979a0cd55fd1447af68bd7503
http://github.com/moodle/moodle/commit/f4a172afdeef89d979a0cd55fd1447af68bd7503
+  4.2 en [zero_default_intro,block_myoverview]
-  4.2 en [zero_createcourses_intro,block_myoverview]
-  4.2 en [zero_nomanagecourses_intro,block_myoverview]
-  4.2 en [zero_nopermission_intro,block_myoverview]