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/Configurable-Non-Player-Arrow-Despawn-Rate.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Configurable Non Player Arrow Despawn Rate
 Can set a much shorter despawn rate for arrows that players can not pick up.
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index 89556dc94a..98049567f4 100644
+index aaa1b60f9..b72da38a7 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 {
@@ -30,7 +30,7 @@ index 89556dc94a..98049567f4 100644
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/EntityArrow.java b/src/main/java/net/minecraft/server/EntityArrow.java
-index 2c0034cf76..44ea39e3d1 100644
+index e83b50ed4..2b829abac 100644
 --- a/src/main/java/net/minecraft/server/EntityArrow.java
 +++ b/src/main/java/net/minecraft/server/EntityArrow.java
 @@ -0,0 +0,0 @@ public abstract class EntityArrow extends Entity implements IProjectile {