chore(deps): update dependency google-cloud-core to "~> 1.8.0"

Author: renovate-bot

google-cloud-spanner/Gemfile

@@ -4,7 +4,7 @@ gemspec
 
 gem "autotest-suffix", "~> 1.1"
 gem "gapic-common", ">= 0.25.0"
-gem "google-cloud-core", "~> 1.7.0"
+gem "google-cloud-core", "~> 1.8.0"
 gem "google-cloud-errors", "~> 1.4.0"
 gem "google-cloud-spanner-admin-database-v1", "~> 1.3"
 gem "google-cloud-spanner-admin-instance-v1", "~> 1.5"