Suggestion: Restore displaced lava after a flag has been destroyed or expires.

[TheFlagCourier]

This ticket is a duplicate of https://github.com/TownyAdvanced/Towny/issues/4040 by @Looowi. Title changed for clarity.

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Placing a fence in water is not a problem after Minecraft 1.15, but placing it in lava will remove it, and it's a problem as enemies can place fence in flag wars. Checking for lava and replacing it after the flag disappears would be really nice. --@Looowi