fix(navbar): fix igx-icon padding in Indigo theme (20.1.x) (#16698)

* fix(navbar): move icon padding to icon-button elements only

* fix(navbar): add 'igc'  selector

---------

Co-authored-by: Simeon Simeonoff <sim.simeonoff@gmail.com>

Author: adrianptrv

projects/igniteui-angular/src/lib/core/styles/components/navbar/_navbar-theme.scss

@@ -117,6 +117,13 @@
         display: flex;
         align-items: center;
 
+        @if $variant == 'indigo' {
+            igc-icon-button,
+            [igxIconButton] {
+                padding: rem(6px);
+            }
+        }
+
         igx-icon,
         igc-icon {
             --component-size: #{if($variant == 'indigo', 2, 3)};
@@ -128,7 +135,6 @@
             @if $variant == 'indigo' {
                 width: auto;
                 height: auto;
-                padding: rem(6px);
             }
         }