chore(main): release 0.304.0 (#8639)

Author: release-please[bot]

VERSION

@@ -1 +1 @@
-1.105.1
+1.106.0

src/SpannerClient.php

@@ -118,7 +118,7 @@ class SpannerClient
     use LROTrait;
     use ValidateTrait;
 
-    const VERSION = '1.105.1';
+    const VERSION = '1.106.0';
 
     const FULL_CONTROL_SCOPE = 'https://www.googleapis.com/auth/spanner.data';
     const ADMIN_SCOPE = 'https://www.googleapis.com/auth/spanner.admin';