fix(query-builder): fix style sample button color and height (#3537)

Co-authored-by: INFRAGISTICS\IPetrov <IPetrov@infragistics.com>
Co-authored-by: Galina Edinakova <gedinakova@infragistics.com>

Author: ivanvpetrov

src/app/interactions/query-builder/query-builder-style/query-builder-style.component.scss

@@ -91,6 +91,10 @@ $custom-drop-down: drop-down-theme($schema: $dark-material-schema,
                 color: $yellow
             }
 
+            .igx-icon-button--flat{
+                height: 32px;
+            }
+
             .igx-filter-tree__inputs-actions igx-icon {
                 color: $yellow
             }
@@ -103,6 +107,18 @@ $custom-drop-down: drop-down-theme($schema: $dark-material-schema,
                 color: $muted-yellow
             }
 
+            .igx-filter-tree__expression-actions igx-icon {
+                color: $yellow !important
+            }
+
+            .igx-filter-tree__expression-actions igx-icon:hover {
+                color: $muted-yellow
+            }
+
+            .igx-filter-tree__expression-actions igx-icon:focus {
+                color: $muted-yellow
+            }
+
             .igx-filter-contextual-menu {
                 border: 1px solid $yellow
             }