Remove unnecessary resetting of left round (twbs#26238)

scss/_input-group.scss

@@ -47,8 +47,7 @@
 
     &:not(:last-child) .custom-file-label,
     &:not(:last-child) .custom-file-label::after { @include border-right-radius(0); }
-    &:not(:first-child) .custom-file-label,
-    &:not(:first-child) .custom-file-label::after { @include border-left-radius(0); }
+    &:not(:first-child) .custom-file-label { @include border-left-radius(0); }
   }
 }