feat(combo): fix initial combo height

Author: didimmova

projects/igniteui-angular/src/lib/core/styles/components/combo/_combo-theme.scss

@@ -100,7 +100,7 @@
     %igx-combo__content {
         position: relative;
         overflow: hidden;
-        max-height: calc(var(--size) * 10);
+        max-height: calc(var(--size) * 6);
 
         &:focus {
             outline: transparent;