update helm repo before intalling mariadb

[olikyr]

Description of your changes

We encountered the following error in the CI pipeline on master.

>>>>>>> installing MariaDB with no TLS
secret/mariadb-creds created
index.go:346: skipping loading invalid entry for chart "airflow" "" from https://charts.bitnami.com/bitnami: validation: chart.metadata.name is required
index.go:346: skipping loading invalid entry for chart "airflow" "" from /home/runner/.cache/helm/repository/bitnami-index.yaml: validation: chart.metadata.name is required
Error: INSTALLATION FAILED: failed to download "bitnami/mariadb" at version "11.3.0"

Fixes #
Apply a helm repo update before installing.

I have:

• [ x ] Read and followed Crossplane's contribution process.
• [ x ] Run make reviewable to ensure this PR is ready for review.

How has this code been tested

make clean
make build
make reviewable
make e2e