replace occurence of AssignExprCfgNode for Oj as well

Author: p-

ruby/ql/lib/codeql/ruby/security/UnsafeDeserializationCustomizations.qll

@@ -180,8 +180,7 @@ module UnsafeDeserialization {
      * Gets the value being assigned to `Oj.default_options`.
      */
     DataFlow::Node getValue() {
-      result.asExpr() =
-        this.getArgument(0).asExpr().(CfgNodes::ExprNodes::AssignExprCfgNode).getRhs()
+      result = this.getArgument(0)
     }
   }
 
@@ -266,7 +265,7 @@ module UnsafeDeserialization {
      * Gets the value being assigned to `Ox.default_options`.
      */
     DataFlow::Node getValue() {
-      result =  this.getArgument(0)
+      result = this.getArgument(0)
     }
   }