fix(toast): update style direction to flex-direction (angular#11169)

In the component md-toast the property "direction" is set to "row". It seems like it's intended to use "flex-direction", as "row" is not a valid value for the property direction, which should indicate the direction of text.

This doesn't change the behaviour of md-toast, just cleaning up a small typo :)

src/components/toast/toast.scss

@@ -26,7 +26,7 @@ md-toast {
 
   .md-toast-content {
     display: flex;
-    direction: row;
+    flex-direction: row;
     align-items: center;
 
     max-height: 7 * $toast-height;