docs(adr-003): drop the stale capability renewal wording in capability delegation #2373

Problem

ADR 003 § Capability delegation describes capability expiry two ways that don't agree. Both lines are on main (cdd1db5e).

Line 49 suggests the owner can renew a capability:

The expiry retires the key when the owner does not renew it.

Line 51 says renewal does not exist. Capability registration is write-once per (poolId, signer):

The first capability that lands on-chain for a signer fixes its cap and expiry. The contract ignores every later capability for that signer. The protocol has no capability renewal. To change the terms, the owner authorizes a new signer key.

The write-once rule is the current design. The pool-solvency read-fault and clamp bullets depend on it, and the SignerCapExhausted / CapabilityExpired recovery text says each recovery names a new signer key. Line 49 is left over from an earlier version.

Fix

Reword line 49 so it no longer implies renewal. For example:

The expiry retires the key; to extend or change its terms, the owner authorizes a new signer key.

Also check line 546 (a short-TTL \expiry` plus non-renewal retires the key`). It is consistent in meaning, but it could point to § Capability delegation so the write-once rule has one home.

Context

Found while resyncing docs.decdn.org with the ADRs in decdn/website#271. The docs follow the write-once rule.