Remove printer friendly clean display option, following a proposal of

Remove printer friendly clean display option, following a proposal of
mine on the devel list to which no objections arose. The option is
totally unclear to end users, and has very little impact. The cleaning
is now always done.
If it turns out this is really missed, or if people really want to turn
the cleaning off, it can of course always be reintroduced - that's
why this is devel.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@8675 7612ce4b-ef26-0410-bec9-ea0150e637f0