Documentation/00-INDEX: remove reference to exception.txt

The exception.txt has been removed from the Documentation directory. So
update the index file for it.

Signed-off-by: Huang Shijie <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/00-INDEX

···
 	- information on EDAC - Error Detection And Correction
 eisa.txt
 	- info on EISA bus support.
-exception.txt
-	- how Linux v2.2 handles exceptions without verify_area etc.
 fault-injection/
 	- dir with docs about the fault injection capabilities infrastructure.
 fb/