Fixed some issues related to z-index and color.

web/pgadmin/dashboard/static/js/WelcomeDashboard.jsx

@@ -72,7 +72,7 @@ const useStyles = makeStyles((theme) => ({
     cursor: 'pointer'
   },
   link: {
-    color: theme.otherVars.stepFg + '!important',
+    color: theme.palette.text.primary + '!important',
   },
   cardColumn: {
     flex: '0 0 100%',

web/pgadmin/misc/file_manager/static/js/select_dialogue.js

@@ -60,7 +60,7 @@ module.exports =  Alertify.dialog('fileSelectionDlg', function() {
 
       // Add our class to alertify
       $(this.elements.body.childNodes[0]).addClass('alertify_tools_dialog_properties');
-
+      $(this.elements.root).css('z-index', 3002);
       $.get(url_for('file_manager.index'), function(data) {
         content.append(data);
       });

web/pgadmin/static/scss/_alertify.overrides.scss

@@ -1,6 +1,5 @@
 /* Overrides alertify js headers */
 .alertify {
-  z-index: 3002;
   position: fixed;
 
   .ajs-header {