Fix docs about usage of only and except options

[oboxodo]

The existing docs lead to non-working code at least with Ruby 2.7.

We need to either make the Array or the Hash explicit in order for it to work:

irb(main):026:0> DatabaseCleaner[:active_record].strategy = :truncation, only: ["users"]
Traceback (most recent call last):
SyntaxError ((irb):26: syntax error, unexpected tLABEL)
...].strategy = :truncation, only: ["users"]
...                          ^~~~~
irb(main):027:0> DatabaseCleaner[:active_record].strategy = [:truncation, only: ["users"]]
=> [:truncation, {:only=>["users"]}]
irb(main):028:0> DatabaseCleaner[:active_record].strategy = :truncation, {only: ["users"]}
=> [:truncation, {:only=>["users"]}]

[codecov[bot]]

Codecov Report

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[viktorianer]

For me, it worked this way to:

DatabaseCleaner[:active_record].strategy = :transaction
DatabaseCleaner.clean_with(:deletion, except: %w(templates))

Either one way or another, it is incorrectly documented and needs to be corrected!

[botandrose]

Thank you, @oboxodo!