Remove outdated Firefox workaround from reindeer in Tabsheet.

Author: Ansku

themes/src/main/themes/VAADIN/themes/reindeer/tabsheet/tabsheet-normal-style.scss

@@ -55,13 +55,6 @@
 	font-size: 14px;
 	font-weight: normal;
 }
-.v-ff & .#{$primaryStyleName}-caption-close{
-	margin-top: -17px;
-}
-
-.v-ff & .#{$primaryStyleName}-caption-close:only-child {
-    margin-top: -1px;
-}
 
 
 .#{$primaryStyleName}-caption-close:hover {

themes/src/main/themes/VAADIN/themes/reindeer/tabsheet/tabsheet-small-style.scss

@@ -52,9 +52,6 @@
 .#{$primaryStyleName}-tabs-bar .#{$primaryStyleName}-caption-close {
 	margin-top: 1px;
 }
-.v-ff & .#{$primaryStyleName}-tabs-bar .#{$primaryStyleName}-caption-close {
-	margin-top: -14px;
-}
 .v-ie9 &, .v-ie10 & {
 	.#{$primaryStyleName}-tabs-bar .#{$primaryStyleName}-caption-close:only-child,
 	.#{$primaryStyleName}-tabs-bar .v-captiontext:first-child + .#{$primaryStyleName}-caption-close {