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/Add-configurable-despawn-distances-for-living-entiti.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Add configurable despawn distances for living entities
 
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index 341038fc4d..3e1f4be10f 100644
+index d0c23915d..c1103bb8f 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 341038fc4d..3e1f4be10f 100644
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/EntityInsentient.java b/src/main/java/net/minecraft/server/EntityInsentient.java
-index 3a96f70d89..a2247fa1dd 100644
+index 7c7d7a123..14b4c1fe6 100644
 --- a/src/main/java/net/minecraft/server/EntityInsentient.java
 +++ b/src/main/java/net/minecraft/server/EntityInsentient.java
 @@ -0,0 +0,0 @@ public abstract class EntityInsentient extends EntityLiving {