Typo in debconf message

[Daniele Forsi]

s/neccessary/necessary/ in the following message:

#. Type: boolean
#. Description
#: ../nvidia-installer-cleanup.templates:1001
msgid ""
"The 'nvidia-installer' program was found on your system.  This is probably "
"left over from an earlier installation of the non-free NVIDIA graphics "
"driver, installed using the NVIDIA *.run file directly.  This installation "
"is incompatible with the Debian packages.  To install the Debian packages "
"safely, it is therefore neccessary to undo the changes performed by 'nvidia-"
"installer'."

-- 
Daniele Forsi