Fix an error for Rails/ReversibleMigration when calling drop_table without any arguments

[Earlopain]

As it happens when you type it

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[koic]

It seems that it should result in no offense as it is still in a state where judgment cannot be made. Also, the description string for the spec appear to have been left as they were copied and pasted.

Suggested change

	it_behaves_like 'offense', 'drop_table(without block)', <<~RUBY
	it_behaves_like 'accepts', 'drop_table (without arguments)', <<~RUBY

[Earlopain]

I switched it over to no offense, that seems fine. And yeah, failed to change the example description.