Remove the 'Middle Name' and 'Suffix' fields

To remove the 'Middle Name' and 'Suffix' fields 
 

In Classic:
1. Click Setup | Customize | User Interface.
2. In the 'Name Settings' section, deselect Enable Middle Names for Person Names and Enable Name Suffixes for Person Names.
3. Click Save.

In Lightning Experience:
1. Click the Gear Icon | Setup | User interface | User interface 
2. In the 'Name Settings' section, deselect Enable Middle Names for Person Names and Enable Name Suffixes for Person Names.
3. Click Save

Note: The Middle Name and Suffix fields are available for the following person objects: Contact, Lead, Person Account, and User.

The Middle Name and Suffix are always available in Apex when it runs in a managed package.