chore: use American spelling in user-facing text

[milanmalhotra]

Found during the v1 to v2 migration rehearsal on 2026-08-18. The import report and several other messages server owners read used British spellings, against house style.

What changed

File	Text
SetHomesV1Importer.java	"differs only in capitalisation" and "colour codes shown as &" in the import report
UserError.java + default-config.yml	movedWhileTeleporting and unsafeHome now say "canceled"
default-config.yml	two comments about '&' colour codes
README.md	two rows of the v1 config mapping table, and two lines of prose
SetHomesTwo.java	a missing word in the v1 collision block

The collision block read "Nothing ever writes to it, but is needed for migrating homes to v2". It now reads "but it is needed".

What was deliberately left alone

• The generated changelog in the README. Those entries are a record of what was published to BukkitDev and the GitHub Releases page, not living text, and the changelog is generated at release rather than hand-edited.
• Past changesets and commit messages, for the same reason.
• isCancelled and setCancelled, which are Bukkit's own API spelling, along with the internal OUTCOME_CANCELLED_MOVED constant and comments describing event cancellation, which match the API deliberately.
• HomeNameValidator.normalise and its call sites. It is an existing identifier rather than user-facing text, so renaming it is a separate call.

Verification

• mvn test: 387 tests, 0 failures, 0 errors, 0 skipped, unchanged before and after.
• No test asserts any of the changed strings, checked before editing.
• An existing config.yml is never rewritten, so a server that has already customized these messages keeps exactly what it set. Only new installs get the corrected defaults.