pmb.helpers.pmaports: Annotate return type for get_list() as list (MR 2431)

I'm not sure why this was annotated as a Sequence rather than list. The
function clearly returns a list, not a Sequence, and the commit that
originally did it[1] provides no justification. This causes problems
with mypy checks in other places, so let's just annotate this as
returning a list.

 [1]: 198f302a

pmb/helpers/pmaports.py

@@ -13,7 +13,6 @@ from pmb.core.pkgrepo import pkgrepo_iter_package_dirs
 from pmb.helpers import logging
 from pathlib import Path
 from typing import Any
-from collections.abc import Sequence
 
 from pmb.meta import Cache
 import pmb.parse
@@ -46,7 +45,7 @@ def _find_apkbuilds(skip_extra_repos=False) -> dict[str, Path]:
     return apkbuilds
 
 
-def get_list() -> Sequence[str]:
+def get_list() -> list[str]:
     """:returns: list of all pmaport pkgnames (["hello-world", ...])"""
     return list(_find_apkbuilds().keys())