Updated GH-100 Notes

[gobinathm]

What does this PR do?

Type of change

• Typo or content error fix
• Content improvement (better explanation, new table, new flashcards)
• New certification notes
• Site/theme/component change
• Worker / API change
• Other:

Certification(s) affected

• Cert: GH-100
• Pages:

Checklist

• The site builds locally without errors (npm run docs:build)
• New content follows the style guide — tables over paragraphs, callouts for exam tips, no emojis in study content
• Flashcard storage-key values are unique (format: <exam-code>-domain-<n>-cards)
• ProgressTracker storage-key is unique (format: <exam-code>-progress)
• Any ${{ }} syntax is wrapped in <div v-pre> to prevent Vue compilation errors
• New certification is added to both the nav and sidebar in .vitepress/config.mts
• WORKER_URL in AIChatBot.vue is set to the production URL (not localhost)