[AIRFLOW-5705] Fix bug in Secrets Backend

[kaxil]

Follow up of #6376 . There were some bugs where the renaming of configs was not applied at all places

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Issue link: AIRFLOW-5705

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cc @dstandish

[kaxil]

I will add more tests as earlier tests didn't cover this Added

[codecov-io]

Codecov Report

Merging #7742 into master will decrease coverage by 0.76%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #7742      +/-   ##
==========================================
- Coverage   86.94%   86.18%   -0.77%     
==========================================
  Files         915      915              
  Lines       44176    44176              
==========================================
- Hits        38407    38071     -336     
- Misses       5769     6105     +336     

Impacted Files	Coverage Δ
airflow/secrets/__init__.py	100.00% <100.00%> (+10.25%)	⬆️
...flow/providers/apache/cassandra/hooks/cassandra.py	21.51% <0.00%> (-72.16%)	⬇️
...w/providers/apache/hive/operators/mysql_to_hive.py	35.84% <0.00%> (-64.16%)	⬇️
airflow/kubernetes/volume_mount.py	44.44% <0.00%> (-55.56%)	⬇️
airflow/providers/postgres/operators/postgres.py	50.00% <0.00%> (-50.00%)	⬇️
airflow/providers/redis/operators/redis_publish.py	50.00% <0.00%> (-50.00%)	⬇️
airflow/kubernetes/volume.py	52.94% <0.00%> (-47.06%)	⬇️
airflow/providers/mongo/sensors/mongo.py	53.33% <0.00%> (-46.67%)	⬇️
airflow/kubernetes/pod_launcher.py	47.18% <0.00%> (-45.08%)	⬇️
airflow/providers/mysql/operators/mysql.py	55.00% <0.00%> (-45.00%)	⬇️
... and 11 more

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[dstandish]

Sorry @kaxil / thanks