Cluster determine slot command name need upper

[yangbodong22011]

The judgment of the name is all uppercase, for example:
https://github.com/redis/redis-py/blob/master/redis/cluster.py#L970

if command in ("EVAL", "EVALSHA"):

Repro code

#!/usr/bin/env python
#-*- coding: utf-8 -*-
from redis.cluster import RedisCluster
host = '127.0.0.1'
port = 30001
user = 'default'
pwd = ""
rc = RedisCluster(host=host, port=port, username=user, password=pwd)
print(rc.execute_command('EVAL', 'return', '0', 'hello'))

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.05% 🎉

Comparison is base (19b55c6) 91.29% compared to head (4bd4324) 91.34%.
Report is 14 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2919      +/-   ##
==========================================
+ Coverage   91.29%   91.34%   +0.05%     
==========================================
  Files         126      126              
  Lines       32391    32335      -56     
==========================================
- Hits        29570    29538      -32     
+ Misses       2821     2797      -24     

Files Changed	Coverage Δ
redis/asyncio/cluster.py	91.66% <100.00%> (ø)
redis/cluster.py	92.81% <100.00%> (ø)

... and 19 files with indirect coverage changes

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