Documentation: security/keys: eliminate duplicated word

Documentation: security/keys: eliminate duplicated word

Drop the doubled word "in".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: linux-integrity@vger.kernel.org
Cc: keyrings@vger.kernel.org
Link: https://lore.kernel.org/r/20200707180414.10467-19-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>