[NFC][LLDB] Remove an unnecessary virtual destructor

DWARFExpression has a virtual destructor but no other virtual methods, so we can safely remove the virtual keyword.

Author: walter erquinigo

lldb/include/lldb/Expression/DWARFExpression.h

@@ -45,7 +45,7 @@ class DWARFExpression {
   DWARFExpression(const DataExtractor &data);
 
   /// Destructor
-  virtual ~DWARFExpression();
+  ~DWARFExpression();
 
   /// Return true if the location expression contains data
   bool IsValid() const;