Simplify statements about authentication of cert information

[aarongable]

• Simplify 3.2.2 to more directly reflect the language used in that section of the BRs
• Replace sections 3.2.3, 3.2.4, and 3.2.5 with "No applicable", because Let's Encrypt does not need to perform authentication of individual identity or validation of authority, and does not include non-verified subscriber information in certificates

Note that this is the first use of "Not applicable." as full section contents in this document. This feels more appropriate than "No stipulation", as we are affirmatively stating that these sections do not concern our operations, rather than saying simply that we choose not to describe our operations in these sections.