Remove the duplicate words 'cannot be' from the zpool.8 man page.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1177
-A device used to cache storage pool data. A cache device cannot be cannot be configured as a mirror or \fBraidz\fR group. For more information, see the "Cache Devices" section.
+A device used to cache storage pool data. A cache device cannot be configured as a mirror or \fBraidz\fR group. For more information, see the "Cache Devices" section.