MDEV-13893/MDEV-12699: Enable encryption.innodb-redo-badkey

The test had been disabled in 10.2 due to frequent failures,
in 5ec9b88e.
After the problems were addressed, we failed to re-enable the test
until now.

mysql-test/suite/encryption/disabled.def

@@ -12,4 +12,3 @@
 
 innodb_scrub            : MDEV-8139 scrubbing does not work reliably
 innodb_scrub_background : MDEV-8139 scrubbing does not work reliably
-innodb-redo-badkey      : MDEV-13893/MDEV-12699 fix recovery of corrupted pages