Bump spongeapi from 7.3.0 to 7.4.0 in /Plan (#2172)

Bumps [spongeapi](https://github.com/SpongePowered/SpongeAPI) from 7.3.0 to 7.4.0.
- [Release notes](https://github.com/SpongePowered/SpongeAPI/releases)
- [Commits](https://github.com/SpongePowered/SpongeAPI/compare/v7.3.0...v7.4.0)

---
updated-dependencies:
- dependency-name: org.spongepowered:spongeapi
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Plan/build.gradle

@@ -68,7 +68,7 @@ subprojects {
         bukkitVersion = "1.13.2-R0.1-SNAPSHOT"
         spigotVersion = "1.13.2-R0.1-SNAPSHOT"
         paperVersion = "1.13.2-R0.1-SNAPSHOT"
-        spongeVersion = "7.3.0"
+        spongeVersion = "7.4.0"
         nukkitVersion = "1.0-SNAPSHOT"
         bungeeVersion = "1.16-R0.4"
         velocityVersion = "3.0.0-SNAPSHOT"