feat!: Drop Rails 6.0 EOL (#680) #3

Job	Run time
action_pack / ubuntu-latest	1m 44s
action_view / ubuntu-latest	2m 9s
active_job / ubuntu-latest	3m 3s
active_model_serializers / ubuntu-latest	1m 11s
active_record / ubuntu-latest	1m 33s
active_support / ubuntu-latest	2m 36s
all / ubuntu-latest	2m 4s
aws_sdk / ubuntu-latest	6m 38s
base / ubuntu-latest	1m 19s
concurrent_ruby / ubuntu-latest	1m 59s
delayed_job / ubuntu-latest	1m 58s
ethon / ubuntu-latest	2m 14s
excon / ubuntu-latest	1m 28s
faraday / ubuntu-latest	4m 7s
grape / ubuntu-latest	5m 0s
graphql / ubuntu-latest	1m 4s
gruf / ubuntu-latest	56s
http / ubuntu-latest	1m 7s
http_client / ubuntu-latest	42s
httpx / ubuntu-latest	3m 28s
koala / ubuntu-latest	38s
lmdb / ubuntu-latest	1m 26s
net_http / ubuntu-latest	1m 25s
rack / ubuntu-latest	1m 32s
rails / ubuntu-latest	2m 7s
restclient / ubuntu-latest	2m 8s
rspec / ubuntu-latest	1m 37s
sinatra / ubuntu-latest	2m 42s
	59m 55s

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