Still discard prepared upgrade after config-only upgrade

### Problem

It is inconvenient for network operators to need to issue a `FREEZE_ABORT` after a config-only upgrade.

But with current behavior, this is necessary, as the prepared upgrade metadata is [only discarded](https://github.com/hashgraph/hedera-services/blob/develop/hedera-node/hedera-mono-service/src/main/java/com/hedera/node/app/service/mono/ServicesState.java#L377) after a software upgrade.

### Solution

Update the linked code fragment to still discard the prepared upgrade metadata after a config-only upgrade.

### Alternatives

_No response_