regression since fdo#70553

Since there was no explanation why this change had been made, I have
reverted it.

Change-Id: I3bf3428d960bf99d4c242d187bf1e2bf62e71aaa

sysui/desktop/menus/math.desktop

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