chore(deps): update dependency google-cloud-spanner to v3.5.0 (#367)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [google-cloud-spanner](https://togithub.com/googleapis/python-spanner) | `==3.4.0` -> `==3.5.0` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-spanner/3.5.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-spanner/3.5.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-spanner/3.5.0/compatibility-slim/3.4.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-spanner/3.5.0/confidence-slim/3.4.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/python-spanner</summary>

### [`v3.5.0`](https://togithub.com/googleapis/python-spanner/blob/master/CHANGELOG.md#&#8203;350-httpswwwgithubcomgoogleapispython-spannercomparev340v350-2021-06-11)

[Compare Source](https://togithub.com/googleapis/python-spanner/compare/v3.4.0...v3.5.0)

##### Features

-   add decimal validation for numeric precision and scale supported by Spanner ([#&#8203;340](https://www.github.com/googleapis/python-spanner/issues/340)) ([aa36c5e](https://www.github.com/googleapis/python-spanner/commit/aa36c5ecf5b0decc6c5c3316cc5bc6b6981d9bf9))
-   add progress field to UpdateDatabaseDdlMetadata ([#&#8203;361](https://www.github.com/googleapis/python-spanner/issues/361)) ([1c03dcc](https://www.github.com/googleapis/python-spanner/commit/1c03dcc182fc96a2ca85b23da99cbcaebfb3fe09))
-   add query statistics package support ([#&#8203;129](https://www.github.com/googleapis/python-spanner/issues/129)) ([6598dea](https://www.github.com/googleapis/python-spanner/commit/6598deade66c8887514a1a6571fffb1bd7b16fd0))

##### Bug Fixes

-   an Aborted exception isn't properly retried ([#&#8203;345](https://www.github.com/googleapis/python-spanner/issues/345)) ([e69e6ab](https://www.github.com/googleapis/python-spanner/commit/e69e6ab5cffd02bc9af6c08dbe9b5f229847d86d))
-   correctly classify select statements that begin with brackets ([#&#8203;351](https://www.github.com/googleapis/python-spanner/issues/351)) ([d526acc](https://www.github.com/googleapis/python-spanner/commit/d526acca4795ebf34867ab4a256413a728fccd93))
-   update to support the open-telemetry status code spec change ([#&#8203;358](https://www.github.com/googleapis/python-spanner/issues/358)) ([0f894f1](https://www.github.com/googleapis/python-spanner/commit/0f894f12622cfa6e38b838eb91e49f256d8d857d))

</details>

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samples/samples/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-spanner==3.4.0
+google-cloud-spanner==3.5.0
 futures==3.3.0; python_version < "3"