Update chaincode container versions in k8s samples

[satota2]

This patch updates chaincode container versions to 2.5 in the following samples:

• test-network-k8s
• full-stack-asset-transfer-guide

Related Issues/PRs

• https://github.com/hyperledger/fabric-samples/issues/1267
• https://github.com/hyperledger/fabric-samples/pull/1266