Some expression language operators seems to produce invalid ruby output
Reproduction:
```console
$ docker pull kaitai/ksv
Using default tag: latest
latest: Pulling from kaitai/ksv
Digest: sha256:444ac8b2ad80a01efa62f09eb3fbce7b2faddb18362017494c5cf3a2eb6d105a
Status: Image is up to date for kaitai/ksv:latest
docker.io/kaitai/ksv:latest
$ docker run -v "$PWD:/share" -it --entrypoint=ksc kaitai/ksv --version
kaitai-struct-compiler 0.10

$ cat ruby_op_bug.ksy
meta:
  id: ruby_op_bug
instances:
  a:
    value: (true == true) == true

$ docker run -v "$PWD:/share" -it --entrypoint=ksc kaitai/ksv -t ruby ruby_op_bug.ksy
$ cat ruby_op_bug.rb
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

require 'kaitai/struct/struct'

unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
  raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end

class RubyOpBug < Kaitai::Struct::Struct
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    self
  end
  def a
    return @a unless @a.nil?
    @a = true == true == true
    @a
  end
end

$ ruby ruby_op_bug.rb
ruby_op_bug.rb:20: syntax error, unexpected ==
    @a = true == true == true
```

Seems parentheses got stripped but `==` is no associative in ruby. For some other operators liks `+` the parentheses seems to be kept.