Disable Content Editor for Specific Pages

Your if condition is wrong and generates a syntax error. You need an logical operator to check for multiple conditions. Therefore your code should look like the following:

if ( $template_file === 'page-custom-one.php' || $template_file === 'page-custom-two.php' ) {
  remove_post_type_support( 'page', 'editor' );
}

You could also check for multiple values with the in_array function like this:

if ( in_array($template_file, ['page-custom-one.php', 'page-custom-two.php'], TRUE) ) {
  remove_post_type_support( 'page', 'editor' );
}

Besides, you should always use strict comparison over loose comparison to prevent unexpected behaviour.