Regenerate native theme .res files for #5170 CSS changes (#5174)

The Native Themes Sync workflow that normally regenerates and commits
these was broken (container-pull + safe.directory bugs, fixed in #5172
and #5173), so the committed Themes/{iOSModernTheme,AndroidMaterialTheme}.res
were never rebuilt after #5170 changed native-themes/ios-modern/theme.css
and native-themes/android-material/theme.css. Regenerated here manually
via scripts/build-native-themes.sh so master's .res match their CSS
sources again.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: shai-almog