chore: release spanner 1.15.0 (#3722)

:robot: I have created a release \*beep\* \*boop\*
---
## [1.15.0](https://www.github.com/googleapis/google-cloud-go/compare/v1.14.1...v1.15.0) (2021-02-24)


### Features

* **spanner/admin/database:** add CMEK fields to backup and database ([47037ed](https://www.github.com/googleapis/google-cloud-go/commit/47037ed33cd36edfff4ba7c4a4ea332140d5e67b))
* **spanner/admin/database:** add CMEK fields to backup and database ([16597fa](https://www.github.com/googleapis/google-cloud-go/commit/16597fa1ce549053c7183e8456e23f554a5501de))


### Bug Fixes

* **spanner:** parallelize session deletion when closing pool ([#3701](https://www.github.com/googleapis/google-cloud-go/issues/3701)) ([75ac7d2](https://www.github.com/googleapis/google-cloud-go/commit/75ac7d2506e706869ae41cf186b0c873b146e926)), refs [#3685](https://www.github.com/googleapis/google-cloud-go/issues/3685)

This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
diff --git a/spanner/CHANGES.md b/spanner/CHANGES.md
index bc76574..0886540 100644
--- a/spanner/CHANGES.md
+++ b/spanner/CHANGES.md
@@ -1,5 +1,18 @@
 # Changes
 
+## [1.15.0](https://www.github.com/googleapis/google-cloud-go/compare/v1.14.1...v1.15.0) (2021-02-24)
+
+
+### Features
+
+* **spanner/admin/database:** add CMEK fields to backup and database ([47037ed](https://www.github.com/googleapis/google-cloud-go/commit/47037ed33cd36edfff4ba7c4a4ea332140d5e67b))
+* **spanner/admin/database:** add CMEK fields to backup and database ([16597fa](https://www.github.com/googleapis/google-cloud-go/commit/16597fa1ce549053c7183e8456e23f554a5501de))
+
+
+### Bug Fixes
+
+* **spanner:** parallelize session deletion when closing pool ([#3701](https://www.github.com/googleapis/google-cloud-go/issues/3701)) ([75ac7d2](https://www.github.com/googleapis/google-cloud-go/commit/75ac7d2506e706869ae41cf186b0c873b146e926)), refs [#3685](https://www.github.com/googleapis/google-cloud-go/issues/3685)
+
 ### [1.14.1](https://www.github.com/googleapis/google-cloud-go/compare/v1.14.0...v1.14.1) (2021-02-09)