[clang-tidy] adjust cppcoreguidelines-owning-memory documentation

[JonasToth]

Summary

A user of the check opened a bugreport and reported that std::exchange
triggers a false positive. I adjusted the doc to include a list of known
(std) constructs that do trigger the issue with templates forgetting the
type alias.

[aaron.ballman]

This is reasonable, though if the list starts getting longer, we should consider trying to fix the bug rather than enumerate them.

docs/clang-tidy/checks/cppcoreguidelines-owning-memory.rst

115

Add a colon after are.

[JonasToth]

I agree.

[JonasToth]

• [Fix] typo

docs/clang-tidy/checks/cppcoreguidelines-owning-memory.rst

.. code-block:: c++
 
   using heap_int = gsl::owner<int*>;
   heap_int allocated = new int(42); // False positive!
 
 The ``gsl::owner<T*>`` is declared as a templated type alias.
 In template functions and classes, like in the example below, the information
 of the type aliases gets lost. Therefore using ``gsl::owner<T*>`` in a heavy templated
 code base might lead to false positives. 
-This limitation results in ``std::vector<gsl::owner<T*>>`` not being diagnosed correctly.
+
+Known code constructs that do not get diagnosed correctly are
+
+- ``std::exchange``
+- ``std::vector<gsl::owner<T*>>``
 
 .. code-block:: c++
 
   // This template function works as expected. Type information doesn't get lost.
   template <typename T>
   void delete_owner(gsl::owner<T*> owned_object) {
     delete owned_object; // Everything alright
   }