refactor: remove unused sass variables in non-theme files (#18911)

We have a couple of unused variables in Sass files which aren't
shipped to the consumers. This means that these variables can
be removed immediately without any deprecation period or breaking
change notice.

Author: devversion

src/material/paginator/paginator.scss

@@ -8,32 +8,8 @@ $mat-paginator-selector-margin: 6px 4px 0 4px;
 $mat-paginator-selector-trigger-width: 56px;
 $mat-paginator-selector-trigger-outline-width: 64px;
 $mat-paginator-selector-trigger-fill-width: 64px;
-
-/** @deprecated Use `$mat-paginator-selector-trigger-width` instead. @breaking-change 8.0.0 */
-$mat-paginator-selector-trigger-min-width: $mat-paginator-selector-trigger-width;
-
-/** @deprecated Unused. To be removed */
-$mat-paginator-range-actions-min-height: 48px;
-
 $mat-paginator-range-label-margin: 0 32px 0 24px;
 
-$mat-paginator-button-margin: 8px;
-$mat-paginator-button-icon-height: 8px;
-$mat-paginator-button-icon-width: 8px;
-
-$mat-paginator-button-increment-icon-margin: 12px;
-$mat-paginator-button-decrement-icon-margin: 16px;
-
-$mat-paginator-button-first-last-icon-width: 14px;
-
-$mat-paginator-button-first-icon-margin: 3px;
-$mat-paginator-button-last-icon-margin: 15px;
-
-
-$mat-paginator-button-first-decrement-icon-margin: 21px;
-$mat-paginator-button-last-increment-icon-margin: 9px;
-
-
 .mat-paginator {
   display: block;
 }

src/material/toolbar/toolbar.scss

@@ -6,11 +6,8 @@ $mat-toolbar-height-mobile: 56px !default;
 $mat-toolbar-row-padding: 16px !default;
 
 /** @deprecated @breaking-change 8.0.0 */
+// TODO: Remove once internal g3 apps no longer depend on this variable. Tracked with: COMP-303.
 $mat-toolbar-height-mobile-portrait: 56px !default;
-/** @deprecated @breaking-change 8.0.0 */
-$mat-toolbar-height-mobile-landscape: 48px !default;
-
-
 
 @mixin mat-toolbar-height($height) {
   .mat-toolbar-multiple-rows {