Remove node edit form field validation
You could do this approach in HOOK_form_alter. Depending on validation that you want to remove... I provide you a simple example of required fields: Suppose you have an Image field that it's required, you could make it unrequired using the following:

$form['field_image']['widget']['0']['#required'] =  TRUE;


Also if you want to remove the "Alt field" for a image you could use: 

$form['field_image']['widget']['0']['#alt_field'] =  FALSE;