Bump Silicon/Arm/Mu_Tiano from 991b1fa to c246bf2 (#1920)

Bumps [Silicon/Arm/Mu_Tiano](https://github.com/microsoft/mu_silicon_arm_tiano) from `991b1fa` to `c246bf2`.
- [Release notes](https://github.com/microsoft/mu_silicon_arm_tiano/releases)
- [Commits](microsoft/mu_silicon_arm_tiano@991b1fa...c246bf2)

---
updated-dependencies:
- dependency-name: Silicon/Arm/Mu_Tiano
  dependency-version: c246bf25b9cd880ffc7c5dc74248996333fdcb40
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]