Add --dependency-update flag to fetch dependencies before installing …

…quickstart (#2135)


**What this PR does / why we need it**:

**Which issue(s) this PR fixes**:

Fixes #

**Does this PR introduce a user-facing change?**:
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This PR was merged by Kapetanios.

docs/content/en/docs/quickstart/_index.md

@@ -26,7 +26,7 @@ cd manifests
 ### 2. Installing control plane
 
 ``` console
-helm -n pipecd install pipecd ./manifests/pipecd --create-namespace \
+helm -n pipecd install pipecd ./manifests/pipecd --dependency-update --create-namespace \
   --values ./quickstart/control-plane-values.yaml
 ```