Documentation/kernel-parameters: remove inttest parameter

According to grep I see no users:
| #git grep inttest
| Documentation/kernel-parameters.txt:    inttest=        [IA-64]

The parameters itself has no description what it supposed to do.
According to the history tree, it was introduced in "[PATCH] Updated
Documentation/kernel-parameters.txt" ("10414c6d"). By that time that
parameter had an user. It was removed later by "[PATCH] ia64: SGI SN
update" ("c6bacd50") by Jesse Barnes himself.

Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: Tony Luck <tony.luck@intel.com>

Documentation/kernel-parameters.txt

@@ -1071,8 +1071,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			no_x2apic_optout
 				BIOS x2APIC opt-out request will be ignored
 
-	inttest=	[IA-64]
-
 	iomem=		Disable strict checking of access to MMIO memory
 		strict	regions from userspace.
 		relaxed