Rename baby zombie movement config option

This option does not set the absolute speed of the entity as the name
implies. It sets a modifier. The default (vanilla) value of `0.5` sets
the baby zombie to move at 50% faster than the base speed.

A negative value like `-0.4` would set them to move at 40% slower.

There should be no functional changes as a result of this change, it's
just clarifying the config name.

Spigot-Server-Patches/Allow-for-toggling-of-spawn-chunks.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Allow for toggling of spawn chunks
 
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index 3e1f4be10f..3f734327c0 100644
+index c1103bb8f..625e75f93 100644
 --- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 +++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 @@ -0,0 +0,0 @@ public class PaperWorldConfig {
@@ -20,7 +20,7 @@ index 3e1f4be10f..3f734327c0 100644
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index 2a0a7f2480..85056a7b1f 100644
+index 67cfcdd60..864d0dd00 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ public abstract class World implements IIBlockAccess, GeneratorAccess, AutoClose