Cut airline show_tab_type command redundancy

It's line 12

themes/airline.vim

@@ -13,7 +13,6 @@ let g:airline#extensions#tabline#show_tab_type = 0
 let g:airline#extensions#tabline#show_tab_nr = 0
 let g:airline#extensions#tabline#fnamecollapse = 1
 
-let g:airline#extensions#tabline#show_tab_type = 0
 let g:airline#extensions#tabline#buffers_label = ''
 let g:airline#extensions#tabline#tabs_label = ''