chore(*): Apply review comments.

Co-authored-by: Simeon Simeonoff <[email protected]>

Author: MayaKirova

projects/igniteui-angular/src/lib/core/styles/components/grid/_grid-theme.scss

@@ -1341,7 +1341,7 @@
     }
 
     %igx-grid__tr--merged {
-        border-bottom: 0px;
+        border-block-end: 0;
     }
 
     %igx-grid__tr--merged-top {