Replace margin with gap

- This is to keep with the flex spirit
- Another solution might instead be to nest .input and .buttons into
   their own container, then apply the gap property to that container.
   This solves the visually uneven spacing between <img> and .input

flex/06-flex-layout/solution/solution.css

@@ -23,7 +23,6 @@ input {
   border-radius: 16px;
   padding: 8px 24px;
   width: 400px;
-  margin-bottom: 16px;
 }
 
 /* SOLUTION */
@@ -43,6 +42,7 @@ button {
   align-items: center;
   justify-content: center;
   flex-direction: column;
+  gap: 16px;
 }
 
 a {