Fix WorkspaceEdit with both documentChanges and changes. (#368)

Prefer `documentChanges` property over `changes` when both are present
in a WorkspaceEdit, complying to the spec:
https://microsoft.github.io/language-server-protocol/specification#workspaceedit

Author: tsufeki

autoload/lsp/utils/workspace_edit.vim

@@ -1,21 +1,20 @@
 " Applies WorkspaceEdit changes.
 function! lsp#utils#workspace_edit#apply_workspace_edit(workspace_edit) abort
-    if has_key(a:workspace_edit, 'changes')
+    if has_key(a:workspace_edit, 'documentChanges')
         let l:cur_buffer = bufnr('%')
         let l:view = winsaveview()
-        for [l:uri, l:text_edits] in items(a:workspace_edit['changes'])
-            call lsp#utils#text_edit#apply_text_edits(l:uri, l:text_edits)
+        for l:text_document_edit in a:workspace_edit['documentChanges']
+            call lsp#utils#text_edit#apply_text_edits(l:text_document_edit['textDocument']['uri'], l:text_document_edit['edits'])
         endfor
         if l:cur_buffer !=# bufnr('%')
             execute 'keepjumps keepalt b ' . l:cur_buffer
         endif
         call winrestview(l:view)
-    endif
-    if has_key(a:workspace_edit, 'documentChanges')
+    elseif has_key(a:workspace_edit, 'changes')
         let l:cur_buffer = bufnr('%')
         let l:view = winsaveview()
-        for l:text_document_edit in a:workspace_edit['documentChanges']
-            call lsp#utils#text_edit#apply_text_edits(l:text_document_edit['textDocument']['uri'], l:text_document_edit['edits'])
+        for [l:uri, l:text_edits] in items(a:workspace_edit['changes'])
+            call lsp#utils#text_edit#apply_text_edits(l:uri, l:text_edits)
         endfor
         if l:cur_buffer !=# bufnr('%')
             execute 'keepjumps keepalt b ' . l:cur_buffer