Help: Fix link in cmake-buildsystem(7)

One local cross-reference added by commit 835f34949e (Help: Update
cmake-buildsystem(7) build and usage requirements, 2024-04-23) had
incorrect syntax.

Help/manual/cmake-buildsystem.7.rst

@@ -195,7 +195,7 @@ Target Commands
 ---------------
 
 Target-specific commands populate the
-`build specification <Target Build Specification>`_ of `Binary Targets`_ and
+`build specification <Target Build Specification_>`_ of `Binary Targets`_ and
 `usage requirements <Target Usage Requirements_>`_ of `Binary Targets`_,
 `Interface Libraries`_, and `Imported Targets`_.