Fix 3 Rubocops

Author: johnnyshields

lib/onelogin/ruby-saml/response.rb

@@ -300,7 +300,7 @@ def issuers
           end
 
           nodes = issuer_response_nodes + issuer_assertion_nodes
-          nodes.map { |node| Utils.element_text(node) }.compact.uniq
+          nodes.filter_map { |node| Utils.element_text(node) }.uniq
         end
       end
 

lib/onelogin/ruby-saml/saml_message.rb

@@ -20,7 +20,7 @@ class SamlMessage
       ASSERTION = "urn:oasis:names:tc:SAML:2.0:assertion"
       PROTOCOL  = "urn:oasis:names:tc:SAML:2.0:protocol"
 
-      BASE64_FORMAT = %r(\A([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?\Z).freeze
+      BASE64_FORMAT = %r(\A([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?\Z)
       @@mutex = Mutex.new
 
       # @return [Nokogiri::XML::Schema] Gets the schema object of the SAML 2.0 Protocol schema

lib/onelogin/ruby-saml/utils.rb

@@ -27,7 +27,7 @@ class Utils
           |
           (\d+)W                    # 8: Weeks
         )
-      $/x.freeze
+      $/x
       UUID_PREFIX = +'_'
 
       # Checks if the x509 cert provided is expired.