SQLA migration: tests: some of the tests are barfing up some warnings

[justcool393]

tests pass currently... but should be fixed and any other instances should be looked for elsewhere in the codebase.
ref #487

files/tests/test_basic.py: 7 warnings
files/tests/test_child_comment_counts.py: 81 warnings
files/tests/test_no_content.py: 7 warnings
  /service/files/helpers/wrappers.py:28: LegacyAPIWarning: The Query.get() method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The method is now available as Session.get() (deprecated since: 1.4) (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
    v = g.db.query(User).get(id)

files/tests/test_basic.py: 1 warning
files/tests/test_child_comment_counts.py: 28 warnings
  /service/files/classes/comment.py:202: LegacyAPIWarning: The Query.get() method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The method is now available as Session.get() (deprecated since: 1.4) (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
    else: return g.db.query(Comment).get(self.parent_comment_id)

files/tests/test_child_comment_counts.py::test_submission_comment_count
  /service/files/routes/admin.py:281: LegacyAPIWarning: The Query.get() method is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The method is now available as Session.get() (deprecated since: 1.4) (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
    c = g.db.query(Comment).get(comment_id)

files/tests/test_child_comment_counts.py: 20 warnings
files/tests/test_seed_db.py: 26 warnings
  /service/files/helpers/comments.py:144: RemovedIn20Warning: The "columns" argument to Select.with_only_columns(), when referring to a sequence of items, is now passed as a series of positional elements, rather than as a list.  (Background on SQLAlchemy 2.0 at: https://sqlalche.me/e/b8d9)
    .with_only_columns([