chore: pinned dep hash of slsa3 workflow

[cmwylie19]

Description

Fixes https://github.com/defenseunicorns/pepr/security/code-scanning/212

The SLSA 3 Workflow needs a pinned dep.

Here is the pinned dep:

> git ls-remote https://github.com/slsa-framework/slsa-github-generator.git refs/tags/v2.1.0

f7dd8c54c2067bafc12ca7a55595d5ee9b75204a	refs/tags/v2.1.0

Here is the sha sum for tag 2.1.0 in the UI

Related Issue

Fixes #

Relates to #

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Other (security config, docs update, etc)

Checklist before merging

• Unit, Integration, docs, adr added or updated as needed
• Contributor Guide Steps followed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (4eab7f9) to head (a97f6a4).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@     Coverage Diff      @@
##   main   #2803   +/-   ##
============================
============================

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