v2.1: CI: Remove crate patches for downstream SPL jobs (backport of #3416)

[mergify]

Problem

The downstream SPL jobs were disabled in #3414 because the crates weren't being patched properly.

Summary of changes

Since the crates are now being properly patched in solana-labs/solana-program-library#7434, re-enable those jobs! At the same time, remove the patch to bump the curve25519-dalek version.

---

This is an automatic backport of pull request #3416 done by Mergify.

[mergify]

Cherry-pick of f9af09c has failed:

On branch mergify/bp/v2.1/pr-3416
Your branch is up to date with 'origin/v2.1'.

You are currently cherry-picking commit f9af09ccc6.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .github/scripts/downstream-project-spl-common.sh

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/downstream-project-spl.yml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[joncinque]

Even though this change doesn't have a material impact on the code, it will ensure that the downstream jobs stay stable in the 2.1 branch, in case there's another change to the curve25519-dalek dependency. Although we likely don't need this change, it's safer to have it.

[yihau]

🪖

[t-nelson]

@joncinque did we lose the yaml changes in conflict resolution?

[t-nelson]

or is the description just inaccurate for the 2.1 branch? 🤔

[joncinque]

or is the description just inaccurate for the 2.1 branch? 🤔

Just inaccurate description, the jobs were never disabled in v2.1 with #3414 -- should I update the description?

[t-nelson]

or is the description just inaccurate for the 2.1 branch? 🤔

Just inaccurate description, the jobs were never disabled in v2.1 with #3414 -- should I update the description?

that'd probably avoid historical confusion