message: Change `-` to `--` for auth-proxy additionalFlags
diff: @@ -89,7 +89,7 @@ helm install kubeapps bitnami/kubeapps \
  --set authProxy.clientID=my-client-id.apps.googleusercontent.com \
  --set authProxy.clientSecret=my-client-secret \
  --set authProxy.cookieSecret=$(echo "not-good-secret" | base64) \
  - --set authProxy.additionalFlags="{-cookie-secure=false,-oidc-issuer-url=https://accounts.google.com}" \
  + --set authProxy.additionalFlags="{--cookie-secure=false,--oidc-issuer-url=https://accounts.google.com}" \
  ```
  **Example 2: Using a custom oauth2-proxy provider**
  @@ -106,7 +106,7 @@ helm install kubeapps bitnami/kubeapps \
  --set authProxy.clientID=my-client-id.apps.googleusercontent.com \
  --set authProxy.clientSecret=my-client-secret \
  --set authProxy.cookieSecret=$(echo "not-good-secret" | base64) \
  - --set authProxy.additionalFlags="{-cookie-secure=false}"
  + --set authProxy.additionalFlags="{--cookie-secure=false}"
  ```
  **Example 3: Authentication for Kubeapps on a GKE cluster**
  @@ -127,7 +127,7 @@ helm install kubeapps bitnami/kubeapps \
  --set authProxy.clientID=my-client-id.apps.googleusercontent.com \
  --set authProxy.clientSecret=my-client-secret \
  --set authProxy.cookieSecret=$(echo "not-good-secret" | base64) \
  - --set authProxy.additionalFlags="{-cookie-secure=false,-scope=https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/cloud-platform}" \
  + --set authProxy.additionalFlags="{--cookie-secure=false,--scope=https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/cloud-platform}" \
  --set frontend.proxypassAccessTokenAsBearer=true
  ```
  