Revert "regression since fdo#70553"

This reverts commit 12546c85.

Apparently I stirred a hornet's nest with this. And I have already
wasted enough time arguing...

sysui/desktop/menus/math.desktop

@@ -18,7 +18,7 @@
 [Desktop Entry]
 Version=1.0
 Terminal=false
-NoDisplay=true
+NoDisplay=false
 Icon=math
 Type=Application
 Categories=Office;Spreadsheet;Education;Science;Math;X-Red-Hat-Base;X-MandrivaLinux-Office-Other;

sysui/desktop/menus/startcenter.desktop

@@ -18,7 +18,7 @@
 [Desktop Entry]
 Version=1.0
 Terminal=false
-NoDisplay=true
+NoDisplay=false
 Icon=startcenter
 Type=Application
 Categories=Office;X-Red-Hat-Base;X-SuSE-Core-Office;X-MandrivaLinux-Office-Other;