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-portal-search-radius.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Add configurable portal search radius
 
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index be91b11242..320fd07c62 100644
+index 95245a981..1d4ba4703 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 {
@@ -19,7 +19,7 @@ index be91b11242..320fd07c62 100644
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/PortalTravelAgent.java b/src/main/java/net/minecraft/server/PortalTravelAgent.java
-index 6552f9e25e..2f0a8e4bb6 100644
+index 6552f9e25..2f0a8e4bb 100644
 --- a/src/main/java/net/minecraft/server/PortalTravelAgent.java
 +++ b/src/main/java/net/minecraft/server/PortalTravelAgent.java
 @@ -0,0 +0,0 @@ public class PortalTravelAgent {