Update pybind11Tools.cmake (#2419)

CPython configured with `--with-pydebug` could not use `pybind11_add_module`
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 29885ae..809cc58 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -82,7 +82,7 @@
 # https://stackoverflow.com/questions/39161202/how-to-work-around-missing-pymodule-create2-in-amd64-win-python35-d-lib
 if(PYTHON_IS_DEBUG)
   set_property(
-    TARGET pybind::pybind11
+    TARGET pybind11::pybind11
     APPEND
     PROPERTY INTERFACE_COMPILE_DEFINITIONS Py_DEBUG)
 endif()