chore: release storage 1.15.0 (#3984)

diff --git a/storage/CHANGES.md b/storage/CHANGES.md
index 4c122dc..661e0b1 100644
--- a/storage/CHANGES.md
+++ b/storage/CHANGES.md
@@ -1,5 +1,18 @@
 # Changes
 
+## [1.15.0](https://www.github.com/googleapis/google-cloud-go/compare/storage/v1.13.0...storage/v1.15.0) (2021-04-21)
+
+
+### Features
+
+* **transport** Bump dependency on google.golang.org/api to pick up HTTP/2
+  config updates (see [googleapis/google-api-go-client#882](https://github.com/googleapis/google-api-go-client/pull/882)).
+
+### Bug Fixes
+
+* **storage:** retry io.ErrUnexpectedEOF ([#3957](https://www.github.com/googleapis/google-cloud-go/issues/3957)) ([f6590cd](https://www.github.com/googleapis/google-cloud-go/commit/f6590cdc26c8479be5df48949fa59f879e0c24fc))
+
+
 ## v1.14.0
 
 - Updates to various dependencies.