RAS/CEC: Remove a repeated 'an' in a comment

The double `an' in the comment in line 41 is repeated. Remove one of
them.

Signed-off-by: Jason Wang <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/ras/cec.c

···
  * elements entered into the array, during which, we're decaying all elements.
  * If, after decay, an element gets inserted again, its generation is set to 11b
  * to make sure it has higher numerical count than other, older elements and
- * thus emulate an an LRU-like behavior when deleting elements to free up space
+ * thus emulate an LRU-like behavior when deleting elements to free up space
  * in the page.
  *
  * When an element reaches it's max count of action_threshold, we try to poison