CI: aport-lint: use alpine:edge

I was wondering why apkbuild-lint found a bug locally but not in CI:

IC[AL65]:main/postmarketos-ui-phosh/APKBUILD:66:2:non-local 'install' variable in function 'openrc'. Add install scripts to global install variable instead.

The reason is that the we use alpine:latest here. Let's change it to
alpine:edge so we have the most recent abuild-go version that finds the
most APKBUILD linting bugs.

Signed-off-by: Oliver Smith <ollieparanoid@postmarketos.org>
Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8735>

.gitlab-ci.yml

@@ -111,6 +111,9 @@ pytest-commits:
 
 # APKBUILD linting
 aport-lint:
+  # alpine:latest doesn't have the most recent atools-go, which means we would
+  # miss some linting rules that were added upstream. Use alpine:edge instead.
+  image: alpine:edge
   stage: lint
   rules:
     - if: *mr_rule