chore(ci): update smp to 0.20.2 (#22318)

As part of keeping Vector's `smp` up-to-date with latest stable, this
commit updates the `smp` version used in CI from 0.20.1 to 0.20.2.

Signed-off-by: Geoffrey M. Oxberry <geoffrey.oxberry@datadoghq.com>

.github/workflows/regression.yml

@@ -105,7 +105,7 @@ jobs:
       - name: Set SMP version
         id: experimental-meta
         run: |
-          export SMP_CRATE_VERSION="0.20.1"
+          export SMP_CRATE_VERSION="0.20.2"
           echo "smp crate version: ${SMP_CRATE_VERSION}"
           echo "SMP_CRATE_VERSION=${SMP_CRATE_VERSION}" >> $GITHUB_OUTPUT