Update version of bundled helm client
Apparently 2.8.2 didn't support authentication for chart repos; 2.9.1
does.
# NB Helm clients will refuse to play with Tiller that is older. 2.8.2
-# is the first release that had checksums, so it's used.
-HELM_VERSION=2.8.2
-HELM_CHECKSUM=614b5ac79de4336b37c9b26d528c6f2b94ee6ccacb94b0f4b8d9583a8dd122d3
+# is the first release that had checksums; but 2.9.1 appears the first
+# that reliably supports authenticating against chart repos, so that
+# wins.
+HELM_VERSION=2.9.1
+HELM_CHECKSUM=56ae2d5d08c68d6e7400d462d6ed10c929effac929fedce18d2636a9b4e166ba
