Fix github actions python version and support 3.8

[jja725]

No description provided.

[LuQQiu]

self = <alluxio.worker_ring.ConsistentHashProvider object at 0x7f5c36982a10>
worker = WorkerIdentity(version=1, identifier=b'O#\xe7\xa1\xa201\x8a\x91-\xbd\xf8\xf7\x8e\n\xed')
node_index = 0

def _hash_worker_identity(
    self, worker: WorkerIdentity, node_index: int
) -> int:
    # Hash the combined bytes

  hasher = mmh3.mmh3_32()

E AttributeError: module 'mmh3' has no attribute 'mmh3_32'

This is the error in Python 3.7

mmh3 says drop python 3.7 since the lifecycle is Python 3.7 end-of-life (EOL) is 2023-06-27 and Ray will drop the support with the following plan: Ray 2.7 will be the last version that supports Python 3.7. Ray 2.8 will no longer have Python 3.7 wheels for installation.

Leave the decision of supporting python 3.7 to future PRs

[LuQQiu]

@jja725 PTAL, thanks!