fix mixin refactoring

Author: VasilyStrelyaev

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab-panel/_position-bottom.scss

@@ -35,7 +35,7 @@
         $generic-tabs-border-width solid,
         none,
         $generic-tabs-border-width solid,
-        initial,
+        null,
       );
 
       &::after {

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab-panel/_position-left.scss

@@ -27,7 +27,7 @@
         none,
         $generic-tabs-border-width solid,
         none,
-        initial,
+        null,
       );
 
       &::after {

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab-panel/_position-right.scss

@@ -27,7 +27,7 @@
         none,
         $generic-tabs-border-width solid,
         none,
-        initial,
+        null,
       );
 
       &::after {

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab-panel/_position-top.scss

@@ -35,7 +35,7 @@
         $generic-tabs-border-width solid,
         none,
         $generic-tabs-border-width solid,
-        initial,
+        null,
       );
 
       &::after {

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab/_position-bottom.scss

@@ -20,7 +20,7 @@
         null,
         null,
         null,
-        transparent,
+        null,
       );
 
       margin-block-start: -$generic-tabs-border-width;

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab/_position-left.scss

@@ -20,7 +20,7 @@
         $generic-tabpanel-tab-border-transparent,
         null,
         null,
-        transparent,
+        null,
       );
 
       margin-inline-end: -$generic-tabs-border-width;

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab/_position-right.scss

@@ -20,7 +20,7 @@
         null,
         null,
         $generic-tabpanel-tab-border-transparent,
-        transparent,
+        null,
       );
 
       margin-inline-start: -$generic-tabs-border-width;

packages/devextreme-scss/scss/widgets/generic/tabPanel/layout/tab/_position-top.scss

@@ -20,7 +20,7 @@
         null,
         $generic-tabpanel-tab-border-transparent,
         null,
-        transparent,
+        null,
       );
 
       margin-bottom: -$generic-tabs-border-width;