ci: gate merges on the lint job

[joris974]

The check job is the repo's only required status check, and its needs list omits the lint job.
HLint therefore runs on every PR, reports its result, and cannot block a merge — a warning-level
failure is advisory today.

Adding lint to needs closes that without changing the ruleset: check is already the required
context, so nothing in github-vending-machine needs to move.

This is the shape haskell-library-template ships, and the shape freckle/github-vending-machine#263
moved that template's ruleset to. 37 of 43 haskell-package repos have the same gap, either missing the
aggregator entirely or declaring needs: [test] like this one; the three that already require only
check are the cases fixable in one line.

The test failures on this PR are pre-existing, not caused by this change

This diff adds one entry to a needs list and cannot affect a Stack build. The cause is a cold cache:

##[warning]No cache found
Loading cached tree after download from Casa failed on blaze-html-0.9.1.1@sha256:... MissingBlob ...
Error: [S-922] Cannot update index (no local copy)
Error: [S-7282] Stack failed to execute the build plan.

This repo's last full CI run was 2026-08-20. Everything on main since then has been the scheduled
Mergeabot workflow, which does not build. GitHub evicts Actions caches after 7 days of non-use, so this
PR is the first cold rebuild in three weeks, and it failed while populating the package index rather
than on anything in the code.

Re-running the failed jobs cleared it: all 19 checks now pass. So the failure was transient
infrastructure, not a defect in this repo, and nothing needs fixing before lint is gated here.

HLint itself passes (lint is green on this PR), and it is set to fail-on: warning, so merging this
does make existing HLint warnings merge-blocking.