fix : delete `!` in usage part and rewrite the description

subjects/swapargs/README.md

@@ -1,10 +1,11 @@
 ## swap-args
 
 ### Instructions
-Write a program that takes two arguments and swaps them 
-- If the arguments are not 2 print (`'\n'`).
-- Separate the arguments with (`' '`)
-- Print (`'\n'`) at the end of the output.
+
+Write a program that takes two arguments and swaps them.
+- If the number of arguments is different from 2, print (`'\n'`).
+- The arguments must be separated by a withe space.
+- Print (`'\n'`) at the end of the program.
 
 ### Usage
 
@@ -14,5 +15,5 @@ $
 $ go run . 1 2 | cat -e
 2 1$
 $ go run . "World" "Hello" | cat -e
-Hello! World$
+Hello World$
 ```