fix: email link to PK header image

[benfurber]

PR Checklist

• [x] - Commit messages are descriptive, it will be used in our Release Notes
• [ ] - Unit and e2e tests for the changes that have been added (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• [x] Bugfix (fixes an issue)

What is the current behavior?

The PK email template currently links to a now deleted (for whatever reason) asset library.

What is the new behavior?

I've uploaded the same image directly to the firebase image store so this new url shouldn't change.

[codecov[bot]]

Codecov Report

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

Project coverage is 72.24%. Comparing base (a164372) to head (9a0e512). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3830 +/- ## ======================================= Coverage 72.24% 72.24% ======================================= Files 42 42 Lines 1326 1326 Branches 267 267 ======================================= Hits 958 958 Misses 344 344 Partials 24 24 ```

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[cypress[bot]]

onearmy-community-platform    Run #6175

Run Properties:   Passed #6175  •  9a0e512c3c: fix: email link to PK header image

Project	onearmy-community-platform
Branch Review	pull/3830
Run status	Passed #6175
Run duration	04m 12s
Commit	9a0e512c3c: fix: email link to PK header image
Committer	Ben Furber
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	1
Pending	0
Skipped	0
Passing	65
View all changes introduced in this branch ↗︎

[onearmy-bot]

:tada: This PR is included in version 1.211.1 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: