[Fixed] "close button overlay" offset

[Acumane]

The linear gradient behind the tab close button is offset. Repro'ed in at least 134.0 and 133.1

Fixed @ tabsbar.css:276:

/* Close button overlay */
&:not([pinned])::before {
	background: linear-gradient(to left, var(--gnome-tabbar-tab-close-overlay-bg) 50%, transparent);
	border-radius: 0 6px 6px 0;
	content: "";
	height: 100%;
	opacity: 0;
	position: absolute;
	right: 0px;
	transition: background 0.4s linear;
	width: 55px;
	z-index: 99;
}