ACPI: update feature-removal-schedule.txt, /sys/firmware/acpi/namespace is gone

The /sys/firmware/acpi/namespace has already been removed in 2.6.21.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/feature-removal-schedule.txt

@@ -227,20 +227,6 @@ Who:	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 
 ---------------------------
 
-What:	/sys/firmware/acpi/namespace
-When:	2.6.21
-Why:	The ACPI namespace is effectively the symbol list for
-	the BIOS.  The device names are completely arbitrary
-	and have no place being exposed to user-space.
-
-	For those interested in the BIOS ACPI namespace,
-	the BIOS can be extracted and disassembled with acpidump
-	and iasl as documented in the pmtools package here:
-	http://ftp.kernel.org/pub/linux/kernel/people/lenb/acpi/utils
-Who:	Len Brown <len.brown@intel.com>
-
----------------------------
-
 What:	ACPI procfs interface
 When:	July 2007
 Why:	After ACPI sysfs conversion, ACPI attributes will be duplicated