Describe the bug
When starting a v1.21 server (stable release) I get the following in the console:

[21:23:27 WARN]: [org.bukkit.craftbukkit.legacy.CraftLegacy] Initializing Legacy Material Support. Unless you have legacy plugins and/or data this is a bug!
[21:23:41 WARN]: Legacy plugin AdvancedBackups v3.6 does not specify an api-version.

To Reproduce
Steps to reproduce the behavior:

1. Run a v1.21 paper server with v1.21-36 of the AdvancedBackups plugin.
2. See error in console.

Expected behavior
I didn't expect to see the above error in the console due to the plugin reporting that it was compatable with v1.21 of the paper server.

Screenshots
N/A

Versioning (please complete the following information):

• OS: Windows 11
• Minecraft Version(s): 1.21
• Modloader(s): paper
• Mod Version: 3.6

Additional context
N/A.

This issue has been closed - fixed in 3.6.3 which has now been pushed to Curseforge and Modrinth.