Remove unnecessary order_by field in a query (GoogleCloudPlatform#5736)

The start_at_name query has an extra order_by that causes an error.

Removes the following error:

ValueError: The "order by" field path 'state' is not present in the cursor data {'name': 'Springfield'}. All fields sent to ``order_by()`` must be present in the fields if passed to one of ``start_at()`` / ``start_after()`` / ``end_before()`` / ``end_at()`` to define a cursor.

## Description

Fixes #<ISSUE-NUMBER>

Note: It's a good idea to open an issue first for discussion.

## Checklist
- [ ] I have followed [Sample Guidelines from AUTHORING_GUIDE.MD](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md)
- [ ] README is updated to include [all relevant information](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#readme-file)
- [ ] **Tests** pass:   `nox -s py-3.6` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] **Lint** pass:   `nox -s lint` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] These samples need a new **API enabled** in testing projects to pass (let us know which ones)
- [ ] These samples need a new/updated **env vars** in testing projects set to pass (let us know which ones)
- [ ] Please **merge** this PR for me once it is approved.
- [ ] This sample adds a new sample directory, and I updated the [CODEOWNERS file](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/.github/CODEOWNERS) with the codeowners for this sample

Author: jlara310

firestore/cloud-client/snippets.py

@@ -4,7 +4,7 @@
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-#    http://www.apache.org/licenses/LICENSE-2.0
+#     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ -814,7 +814,6 @@ def cursor_multiple_conditions():
     start_at_name = (
         db.collection(u'cities')
         .order_by(u'name')
-        .order_by(u'state')
         .start_at({
             u'name': u'Springfield'
         })