🔧 fix: bump DAGGER_VERSION 0.20.6 → 0.20.8 in CI workflows (#34)

The CLI installed by `dagger-for-github` no longer round-trips
cleanly with the current daggerverse modules at v0.20.6 — the version
handshake fires before `dagger call` reaches user code, so workflow
runs die in the bootstrap step.

Bumps `DAGGER_VERSION` to 0.20.8 across the workflows, matching the
rest of the org's repos that have already moved.

Refs PCC-543

Author: yeazelm

.github/workflows/pr.yaml

@@ -9,7 +9,7 @@ permissions:
   pull-requests: read
 
 env:
-  DAGGER_VERSION: "0.20.6"
+  DAGGER_VERSION: "0.20.8"
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}