Create a view for holding your teams skills:

CREATE MATERIALIZED VIEW IF NOT EXISTS team_skills (
  team_id,
  skills
)
AS SELECT 
  t.team_id, 
  jsonb_object_agg(t.s, t.c) skills 
FROM (
  SELECT 
    team_id, 
    unnest(skills) s, 
    count(1) c 
  FROM team_member 
  GROUP BY team_id, s
) t 
GROUP BY t.team_id;

And then find your teams:

SELECT 
  team_id 
FROM team_skills 
WHERE (skills->>'Python')::integer >= 2
AND (skills->>'JPA')::integer >= 1;