Add margin to prevent "Clear all btn" from moving fix tektoncd#2062

 I add margin to `.bx--btn` class to prevent "Clear all btn" from
 moving.
 The "filter" has  `.bx--tag` class and the "Clear All button" has
 `.bx--btn` class.
 `.bx--tag` class has margin but `.bx--btn` class has not margin. So,
 there was a gap between when there was a "filter" on the left and when
 there was no "filter".
 fix tektoncd#2062

packages/components/src/components/LabelFilter/LabelFilter.scss

@@ -25,7 +25,7 @@ limitations under the License.
     min-height: calc(#{$spacing-08} + #{$button-border-width} + 2px);
     margin-bottom: calc(#{$spacing-05} - #{$button-border-width});
 
-    .bx--tag {
+    .bx--tag, .bx--btn {
       flex-shrink: 0;
       margin: $spacing-05 $spacing-03 0 0;
     }