[Infra] Update actions/cache version for connectors (delta-io#4173)

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#### Which Delta project/connector is this regarding?

- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [ ] Kernel
- [X] Other (INFRA)

## Description

actions/cache@v2 is being deprecated
- actions/cache#1510
- actions/toolkit#1890

This PR job caught the brownout
https://github.com/delta-io/delta/actions/runs/13396661811/job/37417276819?pr=4127

Upgrades connectors workflow which is still on v2.

## How was this patch tested?

CI test suffices.

## Does this PR introduce _any_ user-facing changes?

No

.github/workflows/connectors_test.yaml

@@ -16,7 +16,7 @@ jobs:
           distribution: 'zulu'
           java-version: '8'
       - name: Cache Scala, SBT
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             ~/.sbt