Fix for Issue #27

[morch20]

This PR fixes a critical mixin injection failure in the RealFishing compatibility module. The compatibility mixin targeted an outdated method signature for Mob#finalizeSpawn, causing the Boids mod to crash during game initialization whenever RealFishing was present.

Updating the @at(INVOKE) target descriptor and updating the fishing-real's dependency resolves the issue and restores full compatibility.

Changes:

• Updated Mod version from "2.0.2+1.21" to "2.0.3+1.21"
• Updated the fishing-real dependency from "maven.modrinth:fishing-real:1.9.1-backport" (this is for Minecraft 1.20.1) to "maven.modrinth:fishing-real:1.9.1" (this for Minecraft 1.21.1)
• Updated method signature for Mob#finalizeSpan. This method takes 5 parameters in Minecraft versions 1.20.X, and now has been updated to just 4 parameters to be compatible with Minecraft version 1.21.X

Solves issue #27