nvim: Fix completion sourcing for pandoc files

Fixed source completion, so it automatically changes to turn source
switching *off* for pandoc files (to not automatically invoke bibcite
generation), and *on* for the rest of files.

This was accidentally switched the wrong way round before.

nvim/.config/nvim/plugin/completion-nvim.vim

@@ -39,10 +39,10 @@ augroup pandocCompletion
 augroup end
 fun! SetupPandocCompletion()
   if &ft =~ 'pandoc'
-    let g:completion_auto_change_source = 1
+    let g:completion_auto_change_source = 0
     return
   endif
-  let g:completion_auto_change_source = 0
+  let g:completion_auto_change_source = 1
 endfun
 
 " the completion chains for different filetypes