Change the option name according to newfold standards from showMigrationSteps to nfd_show_migration_steps

[aratidgr8]

Summarize the issue (briefly)

Just tech debt change:
We need to update the DB variable name as per Newfold standards that is used to show next steps after migration completion on plugin dashboard Home page.

Steps to reproduce

1. Go to plugin Home page
2. Check the next steps section

Expected behavior
Update the DB variable name from showMigrationSteps to nfd_show_migration_steps

Screenshots

Bluehost Plugin Version:

• Version: 3.12.1

Browser (with version) & Operating System (with version)

• Browser:
• Operating System:
• Device:

Additional context