Upgrade Workbox to 7.3.0

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 29.45%. Comparing base (604b4c6) to head (4166b32).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1205 +/- ## ========================================== Coverage 29.45% 29.45% Complexity 334 334 ========================================== Files 57 57 Lines 1684 1684 ========================================== Hits 496 496 Misses 1188 1188 ``` | [Flag](https://app.codecov.io/gh/GoogleChromeLabs/pwa-wp/pull/1205/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleChromeLabs) | Coverage Δ | | |---|---|---| | [php](https://app.codecov.io/gh/GoogleChromeLabs/pwa-wp/pull/1205/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleChromeLabs) | `29.45% <ø> (ø)` | | | [unit](https://app.codecov.io/gh/GoogleChromeLabs/pwa-wp/pull/1205/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleChromeLabs) | `29.45% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleChromeLabs#carryforward-flags-in-the-pull-request-comment) to find out more.

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