Remove truncation from OCSP `thisUpdate` about boulder HOT 1 CLOSED

For posterity: there was some discussion about whether this truncation could be desirable, to reduce the amount of attacker-controlled data in an OCSP response, to help prevent same-hash attacks. It has been determined that this truncation does not provide meaningful protection for a number of reasons:

• The amount of attacker-controlled data is already minuscule: even the certificate in question is only referred to by its (random) serial number
• We do not include nonces in our OCSP responses, further reducing the attacker-controlled data
• We do not issue OCSP responses from our Roots, so such an attack could not be used to effectively revoke one of our Intermediates
• We do not (and never have) signed OCSP responses using SHA-1 signatures, and SHA-2 remains unbroken thus far
• If SHA-2 is broken, attackers could use that to issue certificates, arguably a much greater threat than using it to revoke them

from boulder.