Fix NoMethodError on custom ActiveSupport::Deprecation behavior

[r7kamura]

Summary

ActiveSupport::Deprecation.behavior= was supposed to accept any object that responds to call, but in fact its internal implementation assumed that this object could respond to arity, so it was restricted to only Proc objects.

This change removes this arity restriction of custom behaviors.

Other Information

The specification of custom behavior is mentioned in the following comment:

rails/activesupport/lib/active_support/deprecation/behaviors.rb

Lines 75 to 76 in dadf171

	# Sets the behavior to the specified value. Can be a single value, array,
	# or an object that responds to +call+.

Without this change, the test I added would fail as follows.

$ bundle exec ruby test/deprecation_test.rb
Running 61 tests in parallel using 12 processes
Run options: --seed 48446

# Running:

.................................................E

Error:
DeprecationTest#test_custom_behavior:
NoMethodError: undefined method `arity' for #<#<Class:0x00007f406a20d418>:0x00007f406a20d2d8>
    /home/r7kamura/ghq/github.com/rails/rails/activesupport/lib/active_support/deprecation/behaviors.rb:117:in `arity_coerce'
    /home/r7kamura/ghq/github.com/rails/rails/activesupport/lib/active_support/deprecation/behaviors.rb:100:in `block in behavior='
    /home/r7kamura/ghq/github.com/rails/rails/activesupport/lib/active_support/deprecation/behaviors.rb:100:in `map'
    /home/r7kamura/ghq/github.com/rails/rails/activesupport/lib/active_support/deprecation/behaviors.rb:100:in `behavior='
    /home/r7kamura/ghq/github.com/rails/rails/activesupport/lib/active_support/deprecation/instance_delegator.rb:21:in `behavior='
    test/deprecation_test.rb:220:in `test_custom_behavior'


rails test test/deprecation_test.rb:213

...........

Finished in 0.203086s, 300.3660 runs/s, 1240.8561 assertions/s.
61 runs, 252 assertions, 0 failures, 1 errors, 0 skips

[jonathanhefner]

Thank you, @r7kamura! 😃

(Backported to 7-0-stable.)