Merge pull request #7182 from hvitved/csharp/self-assignment-bad-magic

C#: Fix bad magic `Element::fromSource` in context of `SelfAssignment.ql`

Author: hvitved

csharp/ql/lib/semmle/code/dotnet/Element.qll

@@ -14,6 +14,7 @@ class Element extends @dotnet_element {
   string toString() { none() }
 
   /** Gets the location of this element. */
+  pragma[nomagic]
   Location getLocation() { none() }
 
   /**