Upgrade redis dependency to v9

[hgokhale]

We are having some dependency issues so wanted to upgrade redis dependency to V9

All tests are passing after this change

=== RUN TestTokenStore

Test redis token store Test authorization code store ✔✔✔✔✔✔ Test access token store ✔✔✔✔✔✔ Test refresh token store ✔✔✔✔✔✔

18 total assertions

--- PASS: TestTokenStore (0.02s) === RUN TestTokenStoreWithKeyNamespace

Test redis token store Test authorization code store ✔✔✔✔✔✔ Test access token store ✔✔✔✔✔✔ Test refresh token store ✔✔✔✔✔✔

36 total assertions

--- PASS: TestTokenStoreWithKeyNamespace (0.02s) PASS ok github.com/go-oauth2/redis/v4 (cached)