[Auto] Updated Upstream (CraftBukkit)

Upstream has released updates that appear to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

CraftBukkit Changes:
2ffdb31ec Use upstream plexus-compiler-eclipse

Spigot-Server-Patches/Implement-Mob-Goal-API.patch

@@ -21,7 +21,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        </dependency>
      </dependencies>
  
-     <repositories>
+     <!-- This builds a completely 'ready to start' jar with all dependencies inside -->
 diff --git a/src/main/java/com/destroystokyo/paper/entity/ai/MobGoalHelper.java b/src/main/java/com/destroystokyo/paper/entity/ai/MobGoalHelper.java
 new file mode 100644
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000

Spigot-Server-Patches/POM-Changes.patch

@@ -195,8 +195,8 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 -                    <compilerId>eclipse</compilerId>
 -                </configuration>
                  <dependencies>
-                     <!-- we need our custom version as it fixes some bugs on case sensitive file systems -->
                      <dependency>
+                         <groupId>org.codehaus.plexus</groupId>
 diff --git a/src/main/java/org/bukkit/craftbukkit/Main.java b/src/main/java/org/bukkit/craftbukkit/Main.java
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
 --- a/src/main/java/org/bukkit/craftbukkit/Main.java