fix: update doc with POST request for /loginAs (#897)

Author: aclec

_includes/rest/users.md

@@ -629,7 +629,7 @@ Calling the endpoint requires the master key and it returns the same response fo
 
 <div class="language-toggle">
 <pre><code class="bash">
-curl -X GET \
+curl -X POST \
   -H "X-Parse-Application-Id: <span class="custom-parse-server-appid">${APPLICATION_ID}</span>" \
   -H "X-Parse-REST-API-Key: <span class="custom-parse-server-restapikey">${REST_API_KEY}</span>" \
   -H "X-Parse-Master-Key: ${MASTER_KEY}" \
@@ -643,7 +643,7 @@ import json,httplib,urllib
 connection = httplib.HTTPSConnection('<span class="custom-parse-server-url">YOUR.PARSE-SERVER.HERE</span>', 443)
 params = urllib.urlencode({"userId":"abc123"})
 connection.connect()
-connection.request('GET', '<span class="custom-parse-server-mount">/parse/</span>loginAs?%s' % params, '', {
+connection.request('POST', '<span class="custom-parse-server-mount">/parse/</span>loginAs?%s' % params, '', {
        "X-Parse-Application-Id": "<span class="custom-parse-server-appid">${APPLICATION_ID}</span>",
        "X-Parse-REST-API-Key": "<span class="custom-parse-server-restapikey">${REST_API_KEY}</span>",
        "X-Parse-Master-Key": "${MASTER_KEY}",