ExplodedGraph never uses ASTContext, remove it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107388 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Checker/BugReporter.cpp b/lib/Checker/BugReporter.cpp
index 3bcc03f..560953f 100644
--- a/lib/Checker/BugReporter.cpp
+++ b/lib/Checker/BugReporter.cpp
@@ -1403,7 +1403,7 @@
 
   // Create a new (third!) graph with a single path.  This is the graph
   // that will be returned to the caller.
-  ExplodedGraph *GNew = new ExplodedGraph(GTrim->getContext());
+  ExplodedGraph *GNew = new ExplodedGraph();
 
   // Sometimes the trimmed graph can contain a cycle.  Perform a reverse BFS
   // to the root node, and then construct a new graph that contains only