Handbook: fix article errors in Subscription Agreement 1.5

The agreement was drafted with a defined term taking "an" and later
globally replaced with "Quote" without correcting the articles, leaving
12 instances of "an Quote" across 11 lines. Section 2 "Acceptance" also
carries a doubled replacement: "reference to an Quote Quote No."

Corrects the articles to "a Quote" (and "A QUOTE" in the all-caps
warranty disclaimer in 3.4), and removes the duplicated word in the
Acceptance definition so it reads "reference to a Quote No."

Grammar only. No defined terms, obligations, or substantive wording are
changed; every edit is an article correction except the one duplicated
word.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: MichaelBDavis