ruby 2.4: fix OpenSSL::Cipher::Cipher deprecation warning

Change-Id: I6e7ffefc974e51e14e2230b5fc09aeb803d408c3
Reviewed-on: https://gerrit.instructure.com/101399
Tested-by: Jenkins
Reviewed-by: Simon Williams <simon@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

Author: ccutrer

lib/canvas/security.rb

@@ -44,7 +44,7 @@ def self.config
 
   def self.encrypt_password(secret, key)
     require 'base64'
-    c = OpenSSL::Cipher::Cipher.new('aes-256-cbc')
+    c = OpenSSL::Cipher.new('aes-256-cbc')
     c.encrypt
     c.key = Digest::SHA1.hexdigest(key + "_" + encryption_key)[0...32]
     c.iv = iv = c.random_iv
@@ -58,7 +58,7 @@ def self.decrypt_password(secret, salt, key, encryption_key = nil)
     encryption_keys = Array(encryption_key) + self.encryption_keys
     last_error = nil
     encryption_keys.each do |encryption_key|
-      c = OpenSSL::Cipher::Cipher.new('aes-256-cbc')
+      c = OpenSSL::Cipher.new('aes-256-cbc')
       c.decrypt
       c.key = Digest::SHA1.hexdigest(key + "_" + encryption_key)[0...32]
       c.iv = Base64.decode64(salt)