fix: Fix markdown lazy load preview message background color

[liamcho]

Changes

• Fixed markdown lazy load preview message background color

ticket: AC-4525

Additional Notes

Checklist

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[github-actions]

Size Change: -57 B (-0.01%)

Total Size: 618 kB

Filename	Size	Change
./dist/__bundle-46d64517-********.js	4.01 kB	+2 B (+0.05%)
./dist/__bundle-b5ef7de4-********.js	890 B	-1 B (-0.11%)
./dist/index-********.js	304 kB	+25 B (+0.01%)
./dist/index.es.js	170 B	-2 B (-1.16%)
./dist/index.umd.js	289 kB	-27 B (-0.01%)
./dist/Placeholder.noChannels-********.js	182 B	-1 B (-0.55%)
./dist/style.css	9.61 kB	+8 B (+0.08%)
./dist/TokensBody-********.js	9.1 kB	-61 B (-0.67%)

ℹ️ View Unchanged

Filename	Size
./dist/__bundle-7c3d40f4-********.js	21 B
./dist/Placeholder.error-********.js	345 B
./dist/Placeholder.loading-********.js	184 B
./dist/Placeholder.noMessages-********.js	183 B
./dist/PlaceholderCommon-********.js	245 B

_{compressed-size-action}