fix(chips): remove chip bottom margin in sibling chips (#8198)

Author: tinayuangao

src/lib/chips/chips.scss

@@ -7,7 +7,6 @@ $mat-chip-remove-margin-before: 6px;
 $mat-chip-remove-margin-after: -4px;
 
 $mat-chips-chip-margin: 8px;
-$mat-chips-chip-bottom-margin: 3px;
 
 $mat-chip-input-width: 150px;
 $mat-chip-input-margin: 3px;
@@ -29,10 +28,10 @@ $mat-chip-input-margin: 3px;
 
   // Apply a margin to adjacent sibling chips.
   & + & {
-    margin: 0 0 $mat-chips-chip-bottom-margin $mat-chips-chip-margin;
+    margin: 0 0 0 $mat-chips-chip-margin;
 
     [dir='rtl'] & {
-      margin: 0 $mat-chips-chip-margin $mat-chips-chip-bottom-margin 0;
+      margin: 0 $mat-chips-chip-margin 0 0;
     }
   }