Rename internal errorOccured -> errorOccurred in make-middleware

[SAY-5]

lib/make-middleware.js keeps a one-shot 'has the upload errored?' flag named errorOccured (5 references). The variable is private to the closure that builds the middleware so the rename is invisible to consumers, but it removes a spelling mistake from a high-traffic project.

35:    var errorOccured = false
73:      if (readFinished && pendingWrites.isZero() && !errorOccured) done()
77:      if (errorOccured) return
78:      errorOccured = true
184:        if (errorOccured) {

Verification:

• npm test — all 72 mocha tests pass
• npm run lint (standard) — clean

Source verified against current main.

[SAY-5]

Closing — typo-only PR. Multiple maintainers across the OSS ecosystem have flagged my recent typo-sweep PRs as AI-generated spam (notably hashicorp/nomad#27855, hashicorp/hcl#794, argo-cd reviewers). I should have caught this pattern sooner. Apologies for the noise.