chore: update test dependencies

Update chart-testing and kind to the current versions.
diff --git a/test/e2e-kind.sh b/test/e2e-kind.sh
index 525c8ee..dd58583 100755
--- a/test/e2e-kind.sh
+++ b/test/e2e-kind.sh
@@ -4,8 +4,8 @@
 set -o nounset
 set -o pipefail
 
-readonly CT_VERSION=v3.7.1
-readonly KIND_VERSION=v0.17.0
+readonly CT_VERSION=v3.8.0
+readonly KIND_VERSION=v0.18.0
 readonly CLUSTER_NAME=chart-testing
 readonly K8S_VERSION=v1.25.3