Help: Add 3.29 release note for try_compile LINKER_LANGUAGE option

In commit 0f37000304 (try_{compile,run}: add LINKER_LANGUAGE option,
2023-10-12, v3.29.0-rc1~567^2) a release note was accidentally added in
the wrong directory and so was not included in the 3.29 release notes.

Help/dev/try_compile-linker-language.rst

@@ -1,6 +0,0 @@
-try_compile-linker-language
----------------------------
-
-* The :command:`try_compile` and :command:`try_run` commands gained a
-  ``LINKER_LANGUAGE`` option to specify the :prop_tgt:`LINKER_LANGUAGE`
-  target property in the generated test project.

Help/release/3.29.rst

@@ -64,6 +64,10 @@ Commands
 * The :command:`if` command gained new tests ``IS_READABLE``, ``IS_WRITABLE``
   and ``IS_EXECUTABLE`` to check file or directory permissions.
 
+* The :command:`try_compile` and :command:`try_run` commands gained a
+  ``LINKER_LANGUAGE`` option to specify the :prop_tgt:`LINKER_LANGUAGE`
+  target property in the generated test project.
+
 Variables
 ---------