.github: [jepsen] cd inside the container, not outside (#6137)

fixes https://github.com/tendermint/tendermint/runs/1925580432
```
No :main namespace specified in project.clj.
```

.github/workflows/jepsen.yml

@@ -45,5 +45,4 @@ jobs:
         run: ./bin/up --daemon
 
       - name: Run the test
-        working-directory: tendermint
-        run: docker exec -i jepsen-control bash -c 'lein run test --nemesis ${{ github.event.inputs.nemesis }} --workload ${{ github.event.inputs.workload }} --concurrency ${{ github.event.inputs.concurrency }} --tendermint-url ${{ github.event.inputs.tendermintUrl }} --merkleeyes-url ${{ github.event.inputs.merkleeyesUrl }} --time-limit ${{ github.event.inputs.timeLimit }} ${{ github.event.inputs.dupOrSuperByzValidators }}'
+        run: docker exec -i jepsen-control bash -c 'cd tendermint; lein run test --nemesis ${{ github.event.inputs.nemesis }} --workload ${{ github.event.inputs.workload }} --concurrency ${{ github.event.inputs.concurrency }} --tendermint-url ${{ github.event.inputs.tendermintUrl }} --merkleeyes-url ${{ github.event.inputs.merkleeyesUrl }} --time-limit ${{ github.event.inputs.timeLimit }} ${{ github.event.inputs.dupOrSuperByzValidators }}'