NEWS: move GC.compact

From "Implementation improvements" to "Core classes updates".

NEWS

@@ -75,6 +75,17 @@ FrozenError::
       FrozenError in Ruby code, pass it as the second argument to
       FrozenError.new.
 
+GC::
+
+  New method::
+
+    * Added GC.compact method for compacting the heap.
+      This function compacts live objects in the heap so that fewer pages may
+      be used, and the heap may be more CoW friendly. [Feature #15626]
+
+      Details on the algorithm and caveats can be found here:
+      https://bugs.ruby-lang.org/issues/15626
+
 Integer::
 
   Modified method::
@@ -168,15 +179,6 @@ JIT::
 
   * Default value of +--jit-min-calls+ is changed from 5 to 10,000
 
-GC::
-
-  * New `GC.compact` method for compacting the heap.
-    This function compacts live objects in the heap so that fewer pages may
-    be used, and the heap may be more CoW friendly. [Feature #15626]
-
-    Details on the algorithm and caveats can be found here:
-    https://bugs.ruby-lang.org/issues/15626
-
 === Miscellaneous changes
 
 * Require compilers to support C99 [Misc #15347]