Help: Fix version note for CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE

This variable predates 3.0.

Fixes: #21522

Help/command/project.rst

@@ -120,8 +120,6 @@ options are intended for use as default values in package metadata and documenta
 Code Injection
 ^^^^^^^^^^^^^^
 
-.. versionadded:: 3.15
-
 If the :variable:`CMAKE_PROJECT_INCLUDE_BEFORE` or
 :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE_BEFORE` variables are set,
 the files they point to will be included as the first step of the
@@ -135,6 +133,9 @@ they point to will be included as the last step of the ``project()`` command.
 If both are set, then :variable:`CMAKE_PROJECT_INCLUDE` will be included before
 :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE`.
 
+.. versionadded:: 3.15
+  Added ``CMAKE_PROJECT_INCLUDE`` and ``CMAKE_PROJECT_INCLUDE_BEFORE`` variables.
+
 .. versionadded:: 3.17
   Added ``CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE_BEFORE`` variable.