docs: add comments for clarity in indices_sorted_by_descending_values method

lab3_task1_funcation_block_arg/main.rb

@@ -1,4 +1,7 @@
 
+# sort by and sort разница
+# enumurable isn't Module, it's Mixture. What is this?
+
 def indices_sorted_by_descending_values(array)
     array.each_with_index.to_a
       .sort_by { |(element, index)| -element }