Update AZ400_M05_L12_Deployments_using_Azure_Bicep_templates.md

[yashints]

Changing the folder name for bicep files

Related Issue

🢂 Fixes #581

Checklist

Mark completed with "x" between brackets, "[x]", or checking the box once the PR is created:

• [x] Has related GitHub Issue 💥 Create Issue 📝
• [x] Tested it
• [x] Read the PR collaboration guide 👓 Collaboration Guide 📝

Changes proposed in this pull request:

• Changed the folder name to Infra from Bicep

[yashints]

@rob-foulkrod @LuizMacedo a quick fix for folder name in the bicep lab