Fixed file field font color for dark mode JabRef#9340

Author: Rory O'Day

src/main/java/org/jabref/gui/Dark.css

@@ -1,3 +1,4 @@
+
 .root {
     -jr-theme: #2c9490;
     -jr-accent: #255652;
@@ -170,3 +171,7 @@
 .rating > .container > .button.strong {
     -fx-icon-color: -fx-light-text-color;
 }
+
+.file-row-text {
+    -fx-text-fill: -fx-light-text-color;
+}