docs(service-worker): update SW guide to include changes about cache (#43163)

[naveedahmed1]

Update Safety Worker section in Service Worker guide and mention that safety worker also removes the SW caches.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Documentation content changes

What is the current behavior?

Safety worker now also removes the SW caches, this wasn't mentioned in docs

Issue Number: #43163

What is the new behavior?

Update docs to mention that safety worker also removes the SW caches.

Does this PR introduce a breaking change?

• Yes
• No

[gkalpak]

Thx, @naveedahmed1 👍
Can you please incorporate the changes into #43324?

[naveedahmed1]

@gkalpak I have added these changes to #43324 I hope I have done it correctly.

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