Wp Dropdown Category Not Show Current As Title

You can use get_query_var( ) to fetch the current category:

$cat = get_query_var( 'cat' );

You can use this $cat in the exclude parameter of wp_dropdown_categories( ) to hide the current category:

$args = array(
  'show_option_none' => __( 'Select A Category' ),
  'show_count' => 1,
  'exclude' => $cat
);

wp_dropdown_categories( $args );