chore: go mod tidy (#357)

After the previous commit, some (but not all) automations running against this repo
reported that a "go mod tidy" needed to be run. This may be because Ginkgo now has
a specific minimum Go version of 1.23.0, whereas brokerapi only specified 1.23.

Author: blgm

go.mod

@@ -1,6 +1,9 @@
 module code.cloudfoundry.org/brokerapi/v13
 
-go 1.23
+go 1.23.0
+
+toolchain go1.23.7
+
 require (
 	github.com/google/uuid v1.6.0
 	github.com/maxbrunsfeld/counterfeiter/v6 v6.9.0