Remove Enumerable include from Statement class

[adamcrown]

I'm honestly not sure why this was here in the first place. Git blame seems to suggest that maybe it was added when the class was first created in anticipation for something that never materialized or has since been deprecated.

As far as I can tell, Enumerable offers no advantages to the class since Statement doesn't implement #each.

Here's an example of what I'm referring to

client = Mysql2::Client.new
statement = client.prepare('select 1')

statement.respond_to? :first
#=> true
statement.first
#=> NoMethodError: undefined method `each' for #<Mysql2::Statement:0x000055f59aa8b2c8>

statement.respond_to? :any?
#=> true
statement.any?
#=> NoMethodError: undefined method `each' for #<Mysql2::Statement:0x000055f59aa8b2c8>

statement.respond_to? :min
#=> true
statement.min
#=> NoMethodError: undefined method `each' for #<Mysql2::Statement:0x000055f59aa8b2c8>

Also all test pass with Enumerable gone, so it seems reasonable to remove it.

[sodabrew]

Must have been copied in accidentally from the Result class when the original work was done.