Update broken links about page and tutorials ownership page

source/about.rst

@@ -3,7 +3,7 @@ About Vala
 
 **valac**, the Vala compiler, is a self-hosting compiler that translates Vala source code into C source and header files. It uses the GObject type system to create classes and interfaces declared in the Vala source code.
 
-`The syntax of Vala <developer-guides/syntax>`_ is similar to C#, modified to better fit the GObject type system. Vala supports modern language features as the following:
+`The syntax of Vala <https://wiki.gnome.org/Projects/Vala/Syntax>`_ is similar to C#, modified to better fit the GObject type system. Vala supports modern language features as the following:
 
 * Interfaces
 * Properties

source/tutorials/programming-language/main/04-00-advanced-features/04-10-ownership.rst

@@ -4,7 +4,7 @@ Ownership
 Unowned References
 ------------------
 
-Normally when creating an object in Vala you are returned a reference to it.  Specifically this means that as well as being passed a pointer to the object in memory, it is also recorded in the object itself that this pointer exists. Similarly, whenever another reference to the object is created, this is also recorded. As an object knows how many references there are to it, it can automatically be removed when needed. This is the basis of `memory management <developer-guides/memory-management>`_.
+Normally when creating an object in Vala you are returned a reference to it.  Specifically this means that as well as being passed a pointer to the object in memory, it is also recorded in the object itself that this pointer exists. Similarly, whenever another reference to the object is created, this is also recorded. As an object knows how many references there are to it, it can automatically be removed when needed. This is the basis of `memory management <https://wiki.gnome.org/Projects/Vala/ReferenceHandling>`_.
 
 Methods ownership
 -----------------