Bump com.terraformersmc:modmenu from 18.0.0-alpha.8 to 20.0.0-alpha.1

Bumps com.terraformersmc:modmenu from 18.0.0-alpha.8 to 20.0.0-alpha.1.

---
updated-dependencies:
- dependency-name: com.terraformersmc:modmenu
  dependency-version: 20.0.0-alpha.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -15,7 +15,7 @@ forgeEventbusValidator-version = "7.0.5"
 neoforgeVersion = "26.1.2.29-beta"
 
 # Mod dependencies
-modmenu-version = "18.0.0-alpha.8"
+modmenu-version = "20.0.0-alpha.1"
 clothConfigVersion = "26.1.154"
 
 fabric-loom-version = "1.16.1"