fix: back button on Read email template

[rajatpandey441]

Description

For going back to the email templates list page, history.goBack() was used but history object was never defined. I replaced history.goBack() with navigate(/${entity.toLowerCase()}); which is working fine. This approach is also used while pressing Close button.

Related Issues

#802

Steps to Test

1. Go to 'Settings'
2. Click on 'Email Templates'
3. Click on Dropdown in front of any email template > Show
4. Click on back button
5. Notice that, user can go back which was not working previously.

Screenshots (if applicable)

Checklist

• I have tested these changes
• I have updated the relevant documentation
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the codebase
• My changes generate no new warnings or errors
• The title of my pull request is clear and descriptive