Lectern page tag/mech fix

[heypr]

• Coming back to an old PR of mine that I closed because I was too dumb at the time lol: https://github.com/DenizenScript/Denizen/pull/2484

• Deprecates the lectern_page tag & mech as they are one number off, ie If a book on a lectern is on page 14, the tag will return 13. & if you want to change the page on the lectern, you have to set the number to be one number higher than the preferred page.