Sidebar submenu title to use theme colors iso always white

Signed-off-by: Eszter Szucs-Matyas <eszter.szucs.matyas@gmail.com>

.changeset/popular-carrots-love.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core-components': patch
+---
+
+Fixed an issue causing `SidebarSubmenu` text to not follow the theme color

packages/core-components/src/layout/Sidebar/SidebarSubmenu.tsx

@@ -80,7 +80,7 @@ const useStyles = makeStyles<
     title: {
       fontSize: theme.typography.h5.fontSize,
       fontWeight: theme.typography.fontWeightMedium,
-      color: theme.palette.common.white,
+      color: theme.palette.navigation.color,
       padding: theme.spacing(2.5),
       [theme.breakpoints.down('xs')]: {
         display: 'none',