fx140: fix cutoff progressWindow on linux (#5462)

Resize the window to fit content on load after the
header is rendered. If the window is resized on
DOMContentLoaded, nothing is rendered yet and the
window will look cutoff on Linux.

Addresses #5453

chrome/content/zotero/progressWindow.xhtml

@@ -47,6 +47,5 @@
 	<script>
         var { Zotero } = ChromeUtils.importESModule("chrome://zotero/content/zotero.mjs");
         Services.scriptloader.loadSubScript("chrome://zotero/content/titlebar.js", this);
-		window.addEventListener("DOMContentLoaded", () => window.sizeToContent())
 	</script>
 </window>

chrome/content/zotero/xpcom/progressWindow.js

@@ -473,6 +473,8 @@ Zotero.ProgressWindow = function (options = {}) {
 		_deferredUntilWindowLoad = [];
 		_deferredUntilWindowLoadThis = [];
 		_deferredUntilWindowLoadArgs = [];
+
+		_progressWindow.sizeToContent();
 	}
 	
 	function _move() {